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Palindromic Numbers
beyond base 10 Page 1
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rood Various Palindromic Sums


Introduction

Palindromic numbers are numbers which read the same from
 p_right left to right (forwards) as from the right to left (backwards) p_left
Here are a few random examples : 7, 3113, 44611644

  1. Go directly to the Base 2 to Base 60 - with gaps - Tables topic
  2. Go directly to the Base 2 Messages topic


led Palindromic in Base 10 and Bases 2 to 60 - with gaps led Tables led

Index Nr

Also palindromic
in base 2 (binary)
A007632

L base 10

L base 2

Next > [183]
183979425852908831095625676590509567652659013880925852497955183
182799251573930069268158338863736883385186296003937515299755183
181598210776723015738823401141914110432883751032767701289555182
180575035268085563259767904058185040976795236558086253057555182
179550013092995264202596149939893994169520246259929031005555182
178537581057012832667042637846564873624076623821075018573555182
177161025037223750639457245622122654275493605732273052016155181
17614160832214049981955813008998003185591899404122380614154177
1759826956806162649079044347191743440970946261608659628953177
1749697433365879869818660045959540066818968978563334796953177
1737410719367998947635063219252912360536749899763917014753176
1723804268201513874247643066282660346742478315102862408353175
1711429080026130929795016072060270610597929031620080924153174
1701158340850135409607322742919247223706904531058043851153173
169332945697934480307232137733773123270308443979654923352172
168189450091914974118478389466498387481147941919005498152171
167167137655962276538005013311331050083567226955673176152171
16654659055038816956906625534355266096596188305509564551169
16554488990162542241782586209026852871422452610998844551169
16434975509525139048267223441443227628409315259055794351168
16330871451329049281732721651561272371829409231541780351168
16212842679910779731236509099909056321379770199762482151167
161914268730651877446829025852092864477815603786241949163
160710924297050261064911517871511946016205079242901749163
159187389335516699661190673537609116699661553398378149161
15859781736587048046249684664869426408407856371879548159
15750218665312803287949336116339497823082135668120548159
15610273564437996321886103113016881236997344653720148157
1557873769607914863131616919616131368419706967378747156
1547495315210345616926314828413629616543012513594747156
1537283003374881572224068111860422275188473300382747156
1527222451273765734414864343468414437567372154222747156
1515624393999400543219160040061912345004999393426547156
1503675592587453421971518575815179124354785295576347155
1491642215900106137684791737197486731601009512246147154
1481232889953189705917173111371719507981359988232147154
147933538832458615602684333348620651685423883533946153
146531893503276610471180799708117401667230539813546152
14590324048680907340709695969070437090868404230945150
14470640032528992699385343435839962998252300460745149
14355701937094119961225858585221699114907391075545149
142910154776775754772502120527745757767745101943143
141734277951397882724548484542728879315977243743143
140338157842070460300161316100306407024875183343142
139181606034479128570886968807582197443060618143141
13890535763073246383343663433836423703675350942140
13759594359862632080790550970802362689534959542139
13630961243190727441854444581447270913421690342138
13517034181515345319715445179135435151814307142137
13413903535144336769976006799676334415353093142137
13312879566967334438177007718344337696659782142137
1329880146634860007999212999700068436641088941137
1315654585830666708792343297807666038585456541136
1303809042117645023377848773320546711240908341135
1293163675976402479420454024974204679576361341135
1281432742521635495126414621594536125247234141134
127711490795092017392455429371029059709411740133
126163458714148851571288217515884141785436140131
125101742176618944510299201544981667124710140130
12477360961819830709759579070389181690637739130
12355170006199840524557554250489916000715539129
12213167445701433021869681203341075447613139127
12112419242135047130072700317405312429142139127
12012224082400223454595954543220042804222139127
1193219015823310110502205011013328510912338125
118997038745499189649194698199454783079937123
117970799914271798490709489717241999707937123
116589389008011598424442489511080098398537123
115168182472583139042824093138527428186137121
114132347545700889596569598800754574323137120
11399802111931818984224898181391112089936120
11279439783264272254004522724623879349736120
11171008423044646995005996464403248001736120
11013912435570164072002704610755342193136117
1099675472097753271070172357790274576936117
1089428584871780514030415087178485824936117
1077675977831193832545238391138779576736116
1065407494054172508878805271450494704536116
1051082762843003964060469300348267280136114
1041065209900655276666672556009902560136114
103993252540228469577596482204525239935113
102148086956396010077001069365968084135111
101140946088414794300349741488064904135111
10057978210097591739371957900128797534109
9933299715642255546455522465179923333109
9818872649303645033305463039462788133108
97715568167610483538401676186551731103
96339074164633138183133646147093331102
95111579203506083338060530297511131100
943780597874646777764647879508733099
93565323456590722270956543235652996
92306584648222253522228464856032995
91300002581511732371151852000032995
90197562912441273721442192657912994
89178698061421842481241608968712994
8816090610983350053389016090612891
877952806296912021969260825972790
865529639562701410726593692552789
855320791612514341521619702352789
84Prime Curios!    3907145050916661905054170932789
833510953314283538241335901532789
821387583213837973831238578312787
81508245138511881158315428052686
8074757030798707897030757472583
7972609886885202588688906272583
7858129885630131036588921852583
7712192281587010785182291212581
7611943137613939316731349112580
7511304860748171847068403112580
74942618055838385508162492377
73929134017759577104319292377
72729280881958591880829272376
71174619989486849899164712374
705394753281718235749352169
691143541261216214534112167
68947781574224751877492067
67328899417887149988232065
66108797402442047978012064
6596748687232786847691964
6470362671262176263071963
633135581533518553131859
621612061522516021611858
61559526370736259551756
60376299270729926731756
59370787968697870731756
58341044820284401431755
57182794408044972811755
56108196719176918011754
55104575874785754011754
5431489557755984131652
5317937707707739711651
529331383638313391550
515522125352122551549
50341413883141431445
4994848747848491344
48Prime Curios!    72847171748271343
4772275262572271343
4656526222625651343
4519999252999911341
4417940969049711341
4317927040729711341
4214749222947411341
4114138999831411341
4012341040143211341
391365255256311237
381109488490111237
37750151510571137
36324792974231135
35184621264811135
34100509050011134
3374511115471033
3212908809211031
31939474939930
30910373019930
29719848917930
2813500531824
275841485723
265259525723
255071705723
243129213722
231979791721
221934391721
211758571721
20585585620
1973737517
1853835516
1753235516
1639993516
1532223515
1415351514
139009414
127447413
11717310
10585310
9Prime Curios!    31339
89927
73326
6914
5Prime!    713
4Prime!    513
3Prime!    312
2111
1011

Index Nr

Also palindromic
in base 3 (ternary)
A007633

L base 10

L base 3

Next > 10^23
74293973755426245573793922348
73263654507438347054563622347
72122419869869689689142212347
7128742640421124046247822245
708216974000300047961282144
696710286086468068201762144
682774444880808844447722143
671341378357775387314312143
661255565144644156555212143
65656911696446961196562042
64177065900330095607712041
6369424985696589424961940
6240549625606526945041940
61Prime!    31952695303596259131939
6027468272313272864721939
5922838641767146838221939
586592958755785929561838
574246761466416764241837
563541641822814614531837
552484809844890848421837
54651928542458291561736
53216696258526966121735
52210752281822570121735
5119842674476248911633
505341743534714351531
494382222122228341531
48694900440094961430
4768521909125861327
4659722090227951327
4549784717487941327
4446570989075641327
4343200484002341327
4221210101012121326
41812345432181123
40580490940851123
3925183381521020
38885626588919
37520080025919
36387505783919
35239060932918
34211131112918
33123464321917
32Prime!    112969211917
3183155138817
3027711772816
29Prime!    7949497715
287875787715
275737375715
264287824714
254251524714
244219124714
234022204714
222985892714
211521251713
20848848613
19Prime!    93739511
1892929511
1776267511
1675457511
1574647511
1448884510
1329092510
12Prime!    75737
1165636
1048436
924235
821235
7Prime!    15135
612135
5812
4412
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 4
A029961

L base 10

L base 4

Next > 10^34
9971793886408606603306606804688397173457
9851088711989055775577550989117880153456
979948878469284012121048296487884993355
968316890270657104340175607209861383355
956819701636821153335112863610791863355
945822810785057043634075058701822853355
935624969158967710701776985196942653355
923724327163889877677898836172342733355
91600363245443350990533445423630063253
90311976749937045005407399476791133253
8954357416402495929594204614753453152
8818750141034481878184430141057813151
8718712357824266828662428753217813151
8618162180029150343051920081261813151
855453494087346944964378049435453050
84927922161495028205941612297292949
83158210484988802088894840128512947
8277781074915764467519470187772847
816661013790102520109731016662745
805411443828394049382834411452745
793530616983674747638961603532745
783367259436087078063495276332745
77358521446506886056441258532643
7656677402607373706204776652542
7556449777850343058777944652542
7452053666249777942666350252542
7350729391215212512193927052542
7216226333058171850333622612541
712247695532500523559674222439
701492655747233274755629412439
691098950812411421805989012439
68989961974524254791699892339
67599232118502058112329952338
66597375942001002495737952338
65574102648825288462014752338
648742187685258678124782135
638309354516261545390382135
628191778624042687719182135
615427374786068747372452135
603717652231613225671732135
593179206132823160297132135
58439829283553829289342033
57413781143003411873142033
5658081974202479180851932
5554527028343820725451932
5438962030353030269831931
5336146214070412641631931
5236102326171623201631931
51Prime!    12702372353273207211931
501018827966972881011829
49960620454540260691729
48572647764677462751728
47559349500059439551728
46135859635369585311727
4571455722227554171627
449127024542072191525
438159691419695181525
426462192429126461525
41418300770038141423
4056902777209651322
3934454161454431321
3816490616094611321
3714912787219411321
365081522518051220
355068022086051220
34Prime!    739796979371119
33592016102951118
32534060604351118
31517171717151118
30954656459915
29623010326915
2853822835813
275679765712
265614165712
255297925712
245259525712
235226225712
225051505712
213866683711
20Prime!    3826283711
192215122711
181801081711
17506605610
165767558
155565558
145525558
135323558
12799747
1193935
10Prime!    78735
966635
839335
7Prime!    37335
65523
5Prime!    512
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 5
A029962

L base 10

L base 5

Next > 10^65
235995436249307088907047418627747868687477268147407098807039426345996593
234991477843125416046549769826168723278616289679456406145213487741996593
23363286027049261480229209749907724427709947902922084162940720682366492
23232140644258668398705501445014760067410544105507893866852446041236491
23111942987062610226478360385012037730210583063874622016260789249116491
230642469941301077916105636531017117101356365016197701031499642466289
229642469471517820731520699880440440440889960251370287151749642466289
22867260551132448100120759173101212101371957021001844231155062766188
22715372909587776115198521047883595388740125891511677785909273516187
22615328059930469397113172255979222979552271311793964039950823516187
2258833561911988807771542297884011048879224517770888911916533886086
2248553871486357385893488060895988959806088439858375368417835586086
223656119821772055472054646127527257216464502745502771289116565985
222490664709018711978208615357738377535168028791178109074660945984
221465647177816374296512860185609065810682156924736187717465645984
220461932046669364210347250565806085650527430124639666402391645984
219268198893789485038973493992665662993943798305849873988918625984
218268193270097873056483860968486848690683846503787900723918625984
217264294703942411048100700780344430870070018401142493074924625984
216235059934868697912224141915771775191414222197968684399505325984
215235051017593361154554436412823282146344554511633957101505325984
214231107161424919830430066071346431706600340389194241617011325984
21399393190189036492875366371429924173663578294630981091393995883
21296635329814314291835774557531135755477538192413418923536695883
2113239929660098237649298907408880470989294673289006692993235781
2101476073877386482860085227265556272258006828468377837067415781
2091474794996046084335011500323932300511053348064069949747415781
2081433886629883237408253836286468263835280473238892668833415781
2071433210239502910194417628709590782671449101920593201233415781
2061198632976583300746542261080008016224564700338567923689115781
2051196285708305603904627052686568625072640930650380758269115781
204Prime!    72781756772491967117815954111459518711769194277657187275579
20372733744929844323275793332565233397572323448929447337275579
20272226642318532278873109732313237901378872235813246622275579
20164327668629549317308633032101230336803713945926866723465579
200857165262259659801811660631360661181089569522625617585376
199857160179411731232897340178710437982321371149710617585376
198857160174774302760817583130313857180672034774710617585376
197828041674877451279878271797971728789721547784761408285376
19646774020181327791602287809908782206197723181020477645274
1958422730896436514247463893439836474241563469803722485173
1948422730844331048374346104840164347384013344803722485173
1938422269149446324536203708680730263542364494196222485173
192148664151788041232580164554610852321408871514668415071
191144533033040945826133771001773316285490403303354415071
1906499362417515913231068055086013231951571426399464869
1896448634006262590883600133100638809526260043684464869
188189464679781072525527073707255252701879764649814767
187184433846070661535669826289665351660706483344814767
186154317930589517667201878781027667159850397134514767
185150883448150414211756638366571124140518443880514767
184150838886088390642818125218182460938806888380514767
1836286970359255785526168886162558755295307968264565
1826232538387472883104888988840138827478383523264565
1816232061136314617559354545395571641363116023264565
1804537498412311671440636563604417611321489473544564
1794535115385056035874956265947853065058351153544564
1782996108066965194088254345288049156966080169924564
1772996103837272660169346464396106627273830169924564
1762959647018070896360107870106369807081074695924564
1752952824356731354436816761863445313765342825924564
1742662018501283633178171017187133638210581026624564
173989668280610409712797887972179040160828669894463
172989126066184857613106336013167584816606219894463
171840866720071025038399779938305201700276680484463
170812406857135691295538998355921965317586042184463
16960110322867109014812101218410901768223011064362
16842775932552072575844737448575270255239577244361
16742700265085366136022727220631663580562007244361
16642367548313256152927545729251652313845763244361
16542367085008248940325757523049842800580763244361
16424264947586415692647414746296514685749462424361
16324264947066584619895050598916485660749462424361
16221814394761437091445464544190734167493418124361
16121471089668339503711505117305933866980174124361
16021069352942997754745999547457799249253960124361
15921069022811913020455909554020319118220960124361
15814166960655000889216626612988000556069661414361
15714148839729719117673191376711917927938841414361
15610103310965822784284585482487228569013301014361
155645155089914443221352531223444199805515464159
154611531386391397014349434107931936831351164159
1538798789996618782041614028781669998789783956
1528793482622028191298189219182022628439783956
151459582826540260607557060620456282859543854
15098355548374646338696833646473845553893753
14995960457688494586898685494886754069593753
14895052271321108467969764801123172250593753
14784676387705731746555647137507783676483753
14681832255758438020434020834857552238183753
14581459783167634355414553436761387954183753
14481401977993885392323293588399779104183753
1436851206038418013677631081483060215863652
1426021170765662212633621226656707112063652
1412153555471650645844854605617455535123651
1401060071622145517800871554122617006013651
13977480920410621016610126014029084773449
13869502677769508914419805967776205963449
1371868385215463911111936451258386813347
1361861628809096304340369090882616813347
1351861623961119681718691116932616813347
1341591710142840364446304824101719513347
1331519985430038416761483003458991513347
1321519980597219741714791279508991513347
131876533436656453773546566343356783246
13062970244597370030073795442079263145
12962927888053243535342350888729263145
12845724004216653343356612400427543144
1279200490388424500542488309400293043
1268639089703324511542330798093683043
125681238668293643463928668321862942
124607954570356595956530754597062942
123416187511289153519821157816142941
122318918847149456549417488198132941
121314179777870796970787779714132941
120314179725473450543745279714132941
119314160632423812183242360614132941
118310981648664943494668461890132941
117310291547250813180527451920132941
116240559997113862683117999550422941
115146265357709638369077535626412941
114106444614644354534464164446012941
113102333175398122218935713332012941
1127759819106642024660191895772739
1117759394105410001450149395772739
1107759342828618681682824395772739
1096917744584313231348544771962739
1086187627509151515190572678162739
1076131190046331513364009113162739
106186521600168668610061256812637
105156361661519889151661636512637
104156311443077997703441136512637
10387857202890212098202758782536
1026791160497744779406119762435
101897505207573757025057982333
100897500541833381450057982333
99897074424920294244707982333
98893787959518159597873982333
97893737033008003307373982333
96893732353051503532373982333
95869853393917193933589682333
94869806770747470776089682333
93865027590484840957205682333
92865027143789873417205682333
91837323433113113343237382333
90832089756951596579802382333
89832084056472746504802382333
8841854598008800895458142231
8734417317918819713714432231
8620154968350053869451022231
8510730776343343677037012231
8410717275957759572717012231
83692586421771246852962029
82668198149559418918662029
81610343750000573430162029
80221927533883357291222028
7918770262464262077811927
7818726667252766627811927
7718721685282586127811927
7615608906212609806511927
7515603938393839306511927
7415274474080474472511927
73675463234323645761725
72625967519157695261725
71284531463641354821724
70280126394936210821724
69258561011101658521724
68258513775773158521724
6786711621126117681623
6680664492294466081623
6580611139931116081623
646587689798678561522
636533110401133561522
624736969696963741521
614736436463463741521
604499339293399441521
594494882828849441521
584453895959835441521
574453849694835441521
564453362726335441521
553785734243758731521
543744769696744731521
533015374347351031521
522791193839119721521
512069035653096021521
502067254445276021521
492023045154032021521
481762657575626711521
471760718381706711521
461728491819482711521
451721020802012711521
441324124342142311521
431077930803977011521
421077457875477011521
411038247174283011521
401031911311913011521
3977301737103771319
3869890626098961319
3769825787528961319
3666949787949661319
3566481303184661319
3466433696334661319
3361057696750161319
3222282616282221318
31121850581211115
30121147411211115
2967615516761015
2828935539821014
2725968869521014
2625128821521014
25836181638913
24836131638913
23831868138913
22831333138913
21808656808913
2065977956812
1947633674811
1830322303811
1727711772811
1610400401811
1510088001811
141888157
131575157
12122145
1167635
1062635
928234
825234
78823
6612
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 6
A029963

L base 10

L base 6

Next > 10^23
118Prime!    365992338076708332995632329
117334610258596958520164332329
116320466969379739696640232329
115314429836759576389244132329
114275969282750572829695722329
113263876970601060796783622329
11248000629714417926000842228
11139513004203302400315932228
11032286072939939270682232228
1099547052777777725074592127
1086986242236763224268962127
1075159428023632082495152127
1064131103281218230113142127
1051840429276567292404812127
1041014861136463116841012126
103806954525885254596082026
10257615474757474516751925
10152835110464011538251925
1006175994277249957161823
99761238292928321671722
98653324626264233561722
97637999786879997361722
96342834907094382431722
95144598686868954411721
94144410504050144411721
93129075688865709211721
9280208634436802081621
9157966638836669751621
9028065926629560821620
899008935853980091520
885964372827346951519
875857893239875851519
865211519291511251519
854806804440860841519
844223837973832241519
833959218481295931519
823890193639109831519
813596302120369531519
803094916261949031519
792856664646665821519
78Prime!    1552598389525511519
77808390440938081418
76519106226019151418
75414439999344141418
74102687997862011417
7397665606566791317
7282888828888281317
7168738121837861317
7036952020259631317
6936932222239631317
6836914222419631317
6736669262966631317
6618084828480811316
65755356535571114
64717717177171114
63616624266161114
62180135310811114
61124824284211113
60Prime!    112715172111113
5988013310881013
5877865568771013
5771118811171013
5643687786341013
5537331133731013
54342050243911
53310393013911
52290222092911
51Prime!    108151801911
50104888401911
49103656301911
4824466442810
4715266251810
46908180979
45816461879
44698389679
43693439679
42690109679
41579997579
40576667579
39573337579
38548284579
37543334579
36540004579
35518281579
34510001579
33484948479
32459895479
31456565479
30451615479
29429892479
28426562479
27423232479
26309790379
25186768179
2490990968
2380880868
2216886167
217464757
203989356
192202256
18777746
17766745
16144145
1586834
1477734
1343434
1234334
11Prime!    19133
1014133
911133
85523
7Prime!    712
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 7
A029964

L base 10

L base 7

Next > 10^23
81679491174069604711949762328
80654373714495944173734562327
79470195768506058675910742327
78296278369016109638726922327
77243927128957598217293422327
76207225215627265125227022327
75Prime!    177977675197915767797712327
7484211989788887989112482226
739425385326862358352492125
727556670179397107665572125
716171611628782611617162125
705075989249094298957052125
694000037170007173000042125
683977931400600413977932125
672401763992529936710422125
66222448184224818442222023
6591006818535818600191923
6478690476242674096871923
63997390470740937991721
62987098559558907891721
61671229110119221761720
60650450533350540561720
59420742053502470241720
5875847187781748571619
5731798622226897131619
562297163636179221517
552158214241285121517
542080639593608021517
532019460106491021517
52851617557161581417
51741949669491471417
50499294774929941417
49234197667914321416
4888680676086881316
4767509898905761316
4641585636585141315
4529282999282921315
4427453828354721315
43268012021086213154
4224519565915421315
4122640929046221315
4012698808896211315
397753500535771215
384269700796241214
37953650563591113
36910239320191113
35Prime!    907507057091113
34754312134571113
33750161610571113
32657960697561113
31644545454461113
30614549454161113
29458622268541113
28401307031041113
27256994996521113
26858474858911
25657494756911
24638828836911
23485494584911
22466828664911
21230474032910
2061255216810
19Prime!    947074979
18695859679
17659795679
16460206478
15213731278
146565656
13Prime!    1656155
1229233
1124233
1017133
912133
8812
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 8 (octal)
A029804

L base 10

L base 8

Next > 10^34
13160912800526960936639069625008219063438
13011418974151908562265809151479814113437
1299940906045724403130442754060904993337
1288580376809657635153675690867308583337
1278355232833325316561352333823255383337
1265876178430469638983696403487167853337
1255643410932371198189117323901434653337
1243553094074844165256144847049035533337
123898797689571943883491759867978983236
122385254913443660330663443194525833235
121171813774259409999049524773181713235
12037920331971624777426179133029733134
11933772424404770333077404424277333134
11829037954774786060687477459730923134
11719497001084229959922480100794913134
116984448615369755579635168444892933
115794438587257191917527858344972933
114686077052002724272002507706862932
113621199781922969692291879911262932
112363865156912056502196515683632932
111204663539763851583679353664022932
11026749723020796697020327947622831
1096190577876735253767877509162730
1081386680923018681032908668312729
1071071840098204440289004817012729
106822686629176446719266862282629
105411554311120550211134551142629
10495044112130363031211440592528
10395029176463787364671920592528
10295004657609222906756400592528
10168577765285363582567775862528
10037608490130818031094806732528
9920911035706151607530119022527
9816468199883030388991864612527
978901702680888808620710982427
963156100278644687200165132427
95397526566230326656257932326
94362583401435341043852632325
93Prime!    341257034953594307521432325
92173952596982896952593712325
91158631250242420521368512325
9073932370647746073239372225
8925034988051150889430522224
885799278101110187299752123
875563629984548992636552123
865528683937273938682552123
854946355319091355364942123
844733170020102007133742123
833790807652425670809732123
823755861605150616855732123
813751835974047953815732123
803719118689198681191732123
792026937121612173962022123
78775808549449458085772023
77446431030220301346442022
76323003611881163003232022
7598432077676770234891922
7438000031505130000831921
7336760771666177067631921
7226506269393962605621921
7124454200797002454421921
7012190711696117091211921
691360533588533506311819
681050804699640805011819
67968768274728678691719
66841991484841991481719
65841723615163271481719
64703333415143333071719
63572340172710432751719
62455762103012675541719
61455344305034435541719
60332390247420932331719
596858544144585861517
586831134743113861517
576665515351556661517
563930734143703931517
553599341114399531517
542247856465874221516
531858509990585811516
521127453835472111516
51349269999629431415
50287195555917821415
49139946886499311415
4877121505121771315
4758531434135851315
4652275292572251315
453908944980931213
442943788734921213
43944666664491113
42940298920491113
41208555558021112
4046373373641011
3944808808441011
3844249942441011
3724645546421011
3618203302811011
35799535997910
34719848917910
33532898235910
3213053503199
315536635589
30419891478
29Prime!    197079177
28193539177
27Prime!    149694177
2666006667
2562882667
2420770266
233030355
22Prime!    3010355
212666255
202646255
19Prime!    1333155
181313155
17877845
16366344
1558534
1441433
13Prime!    37333
1233333
1129233
1012133
9912
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 9
A029965

L base 10

L base 9

Next > 10^23
7576237221536635122732672223
7449978784806608487879942223
7330148492119911294841032223
7218950432936639234059812223
7116853804150051408358612223
701046185104240158164012121
69893493495885943943982021
68821488296996928841282021
67532936484334846392352021
665479069833896097451819
651942164055046124911819
641900760277206700911819
63148025543455208411717
62135774784874775311717
61111997012107991111717
60111110593950111111717
5959870787787078951617
5847825371173528741617
571498192129189411515
561492854345829411515
551019040104091011515
54421439009341241415
53412752222572141415
5220819858918021313
5120240999042021313
5020055424550021313
49Prime!    14002323200411313
488273622637281213
4795653356591011
4689011110981011
4554356653451011
4438200028399
4323200023299
4218143418199
4116719176199
406566665689
39336063377
38330303377
37317171377
36316361377
35312221377
34311411377
33Prime!    310601377
32245054277
31244244277
30243434277
29240104277
28188588177
27187778177
26182828177
25172127177
24171317177
23154045177
2262662667
215060555
204232455
192747255
182575255
17688645
1665633
1564633
1455533
1346433
12Prime!    37333
1128233
10Prime!    19133
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 11
A029966

L base 10

L base 11

Next > 10^21
839032530596369503523092121
827713418328182381431772121
816868330761216703386862121
806711367386668376311762120
7978617360171063716871919
7864116826141628611461919
7742446914676419644241918
76642246526256422461717
75627121196911217261717
74568317298927138651717
73566817644467186651717
72544706422246074451717
714639066566093641515
702597993839979521514
692515691819651521514
682182545954528121514
672182103530128121514
662180532923508121514
6547986414689741313
6429260727062921312
6329092787290921312
62425210125241111
61394532354931111
60392760672931111
59Prime!    99945499999
58Prime!    99811189999
5753718173599
5649208029499
5548952598499
5436215126399
5335677765399
52884448877
51883238877
50882028877
49875857877
48874647877
47873437877
46872227877
45871017877
44729292777
43728082777
42574147577
41566766577
40565556577
39564346577
38459395477
37458185477
36442224477
35441014477
34434843477
33337273377
32336063377
31329892377
30Prime!    328682377
29327472377
28326262377
27296869277
26295659277
257515755
246393655
235282555
224929455
214050455
20Prime!    3818355
192696255
1890933
1789833
16Prime!    78733
1567633
1456533
1345433
1234333
1123233
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 12
A029967

L base 10

L base 12

Next > 10^21
613020022642824622002032119
602836310081318001363822119
592168111492429411186122119
58529757699339967579252019
5739671133313331176931918
5633454546464645454331918
5518345929050929543811917
5413121613757316121311917
5313101271383172101311917
529266179666697166291817
514189557433475598141817
504115288477488251141817
49901458916198541091716
48163301827281033611716
4783301072270103381615
4651282882288282151615
4516436003300634611615
44622184114812261413
43101714664171011413
4245386848683541312
413574966947531211
401225077052211211
39731838381371111
38576441446751110
37509927299051110
36362658562631110
35257123217521110
341393223931109
3379621269799
32Prime!    71317131799
3152002002599
3029337339298
2913997993198
2813337333198
27996369977
26836463877
25564146577
24319291377
2364664666
228888855
214393455
203595355
19800844
18111143
17Prime!    79733
1673733
1567633
1461633
1355533
12Prime!    18133
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 13
A029968

L base 10

L base 13

Next > 10^21
869951651778987715615992119
85Prime!    9700154864646845100792119
849600851376267315800692119
839585399083238099358592119
829319536373437363591392119
818325876482628467852382119
803643704587578540734632119
792925037211411273052922119
782772588802420888527722119
771622381400400418322612119
76Prime!    75208593929395802571917
7555448826232628844551917
7440024142999241420041917
7339761493696394167931917
7238987015373510789831917
7128326049393940623821917
7018369057959750963811917
69491644137314461941715
68458504538354058541715
67370794070704970731715
6672733247742337271615
656728048384082761514
646370131613107361514
632379238783297321513
622356048384065321513
61608083113808061413
60543241991423451413
5916249818942611311
5811993090399111311
577896799769871211
56220878780221110
558390660938109
548381551838109
537497557947109
527488448847109
516933223396109
506924114296109
494378778734109
484369669634109
473814444183109
463805335083109
453071001703109
4495240425999
4366866686698
4265635365698
416261162687
404709907487
394416614487
383329923387
372387783287
362317713287
352094490287
342024420287
331305503187
321012210187
31886468877
30290609276
29283238276
28271317276
27237773276
2631111365
255626555
242636254
232545254
222454254
21877844
20677644
19111143
18Prime!    79733
1766633
1657533
1544433
14Prime!    35333
13Prime!    31333
1222233
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 14
A029969

L base 10

L base 14

Next >10^21
787565179663736697156572119
775357290303130309275352119
765310117820802871101352119
75593801935225391083952018
74592363425995243632952018
73269161020000201619622017
72155951837337381595512017
71153195210660125913512017
7073272848585848272371917
6972096110333011690271917
6861589818494818985161917
6761145066010660541161917
6660053596232695350061917
6537373342505243373731917
6435454942383249454531917
635465460333306456451816
62783252777772523871715
61695807923297085961715
60683002825282003861715
59570473632363740751715
58260722183812270621715
57245144447444415421715
56139556486846559311715
5559020371173020951614
547656110801165671513
537565599899556571513
526920211311202961513
516115522722551161513
504757947474975741513
493061499499416031513
482536755455763521513
472360706760706321513
4658133434331851312
4555421797124551312
4455301383103551312
4355074747470551312
4251050707050151312
4139843212348931311
4024280222082421311
3910984454489011311
3810311868113011311
376952566525961211
365499055099451211
355180322308151211
345086288268051211
3317085058071119
32Prime!    14203330241119
3111652825611119
3010476867401119
296758008576109
285736116375109
2759512159598
2656430346598
2553550553598
24981318977
23957875977
22Prime!    904640977
2154664566
2042002465
195909555
183959355
17111143
1699933
1585833
1471733
1346433
1232333
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 15
A029970

L base 10

L base 15

Next > 10^20
73895514578448754155982017
7267479200444002974761917
7167369425646524963761917
7040385829858928583041916
694277918955981977241815
681941767222276714911815
67749401720271049471715
66Prime!    747131847481317471715
65747129065609217471715
64747126635366217471715
632841111511114821513
622836523132563821513
611415272827251411513
60426299999926241412
59407003993007041412
5880048303840081311
5774855353558471311
5673054808450371311
5570732181237071311
5470731525137071311
5369087323780961311
5269072686270961311
5167994151499761311
5066379171973661311
4966248838842661311
4866240242042661311
4764984090489461311
4664983434389461311
4559385676583951311
4411318777813111311
4311310181013111311
426924655642961211
416152211225161211
4020281518202119
3917406960471119
388083223808109
378052662508109
368050880508109
352118008112108
346945549687
334799997487
323939939387
312830038287
302614416287
291757757187
2852772565
2751551565
2648998465
2547777465
2446556465
236757655
226010655
212555254
202363254
19277243
18155143
1797933
1694933
15Prime!    91933
1488833
1385833
1282833
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 16
A029731

L base 10

L base 16

Next > 10^35
143788941919455633763673365549191498873529
142670809325081810626260181805239080763529
141638358825000179434349710005288538363529
140634943396705903366633095076933494363529
139574867921978413466643148791297684753529
138464942890399854056504589930982494643529
137364532105136497141417946315012354633529
136252951305729660829280669275031592523529
135171930908906517371737156098090391713529
1345891796526699933733999662569719853328
1333241930604180580608508140603914233327
1323224343059210540204501295034342233327
1311889803998895230603259889930898813327
1301571245685777069496077758654217513327
1291535709618861678787616881690753513327
128743107825715208338025175287013473227
127472040481695216886125961840402743227
12695785698142713505317241896587593126
12573088557361233222332163755880373126
12410970297724415636514427792079013125
1234945062538437444473483526054943025
122946942840389313139830482496492925
121946353349736762676379433536492925
120921670130754806084570310761292925
119171736816232649462326186371712924
11845262398479454454974893262542823
11743741754799239932997457147342823
11620925770074499994470077529022823
1158752885028889898882058825782723
1143741780873842124837808714732723
1133198952023678587632025989132723
1121077610994246864249901677012722
1111075271756764946765717257012722
110432318870662992660788132342622
109372649895412992145989462732622
10891331296282111282692133192521
10718467811360656063118764812521
106Prime!    18442380587898785083244812521
10518298600704979407006892812521
10410139452561969165254931012520
103663469484892984849643662319
102555824301288821034285552319
101519593011158511103959152319
100478447285970795827448742319
99472720074510154700272742319
98420014907233327094100242319
97360391093989893901930632319
96345701541695961451075432319
95341758251525251528571432319
94285276977110117796725822319
93214710209180819020174122319
92173226662537352666223712319
91156736052603062506376512319
908739548921512984593782118
892646056168586165064622117
881807662944944926670812117
871362286747274768226312117
861341325824942852314312117
851096409712521790469012117
841050868798689786805012117
83707018845115488107072017
82413179670000769713142017
8146161593080395161641916
8038844257161752448831916
7911370810020018073111915
7811184946030649481111915
778873583311338537881815
765358739166193785351815
753730198055089103731815
74706678205028766071714
73646343274723436461714
72326331961691336231714
71320004280824000231714
7050993476674399051614
6916687397793786611613
688163465556436181513
675220130203102251513
665095386668359051513
65Prime!    3979221512297931513
64451133883311541412
63172627557262711411
62143158228513411411
6178881959188871311
6066943676349661311
59Prime!    34056848650431311
5826926676629621311
5724240585042421311
5618068727860811311
5516316454613611311
5412781696187211311
533901899810931210
5256702120765119
5151113531115119
5045961216954119
4943836363834119
4839762526793119
4732442924423119
4630144644103119
4528779897782119
4428586268582119
4326896769862119
4224796974297
4124109014297
40Prime!    19008009197
3916113116197
3811991991197
379454454987
369435534987
359099990987
346743347687
33961616976
32648784676
31561416576
30248584276
29161216176
2884554865
2774994765
2666666665
2551221565
2433333365
23Prime!    9868955
229636955
21Prime!    9404955
209020955
194151454
183959354
17300343
16199143
1597933
14Prime!    78733
1362633
12Prime!    35333
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 17
A097855

L base 10

L base 17

Next > 10^20
7045522046727640225541916
6925525771777177525521915
6815612031888130216511915
677635044800844053671815
663954148711784145931815
653272242077024227231815
641746703899830764711815
63854373641463734581714
62475482625262845741714
61412857017107582141714
60401019636369101041714
59292876217126782921714
58203783490943873021714
5773517550055715371613
5669052702207250961613
559652014041025691513
544066318781366041512
53190384334830911411
52147050220507411411
5142444050444241311
506508800880561210
494942800824941210
484935333353941210
4798794149789119
4691792829719119
4577991919977119
4472603630627119
4368921312986119
4258802720885119
4157431913475119
4030873037803119
392038558302108
3833592953397
3728053508297
3622923292297
3521231321297
3420837380297
3320753570297
3212445442197
3112361632197
3010359530197
2910275720197
283174471387
27883738876
26416561476
25138883175
2433553365
2325665265
2217777165
219424955
206141654
19455443
18288243
1798933
1681833
1576733
1454533
1349433
1225232
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 18
A248889

L base 10

L base 18

Next > 10^20
83414701968888691074142016
8258275803848308572851915
8158129586404685921851915
8057256008939800652751915
7950528172484271825051915
7848048096888690840841915
7734975093838390579431915
7634898555131555898431915
7533773529525925377331915
7425284680404086482521915
7325255416666614552521915
7224324269212962423421915
7123240742606247042321915
7018845844020448548811915
6911297982060289792111915
681047371655617374011814
67182456016106542811713
66112477795977742111713
6547253935539352741613
6446714313313417641613
6334967742247769431613
6215116684486611511613
614277407770477241512
603852818781825831512
59562036886302651411
58353344554433531411
5757644363446751311
5639684121486931311
5533769636967331310
5425576151675521310
53188833338881129
52Prime!    79288288297119
5169675357696119
5059388288395119
4958813031885119
4826965056962119
4714969696941119
4638719178397
45Prime!    38645468397
4438571758397
4337622267397
4232769672397
4132695962397
4022105012297
3922031302297
3819101019197
3711891981197
368884488887
355549945587
345441144587
333938839387
32Prime!    183238175
31140304175
30125452175
2998118965
2885995865
2778228765
2658338565
2526226265
246999654
234666454
222333254
21377343
20211243
19166143
1884833
1768633
1659533
1550533
1434333
1332332
1217132
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 19
A248899

L base 10

L base 19

Next > 10^20
60113304225775224033112015
5996111760393067111691915
5893331208151802133391915
5787051151525151150781915
5685077754909457770581915
5574011307040703110471915
5473827193989391728371915
5365100997595799001561915
5258461941565149164851915
5145021463515364120541915
5043063519292915360341915
4936956532242235659631915
48415308757578035141713
47336706751576076331713
46306769820289676031713
45218588503058858121713
44180576612166750811713
43103653168613563011713
4283286547745682381613
4127944789987449721613
4026966174471669621613
3969768626867961311
3869599262995961311
37246025520642129
36234595595432129
35139103301931129
34127673376721129
33121791197121129
3296060106069119
3187161116178119
3067269596276119
2962558085526119
2847069796074119
2786382836897
2685738375897
2566690966697
2465076705697
2346753576497
2245384835497
21Prime!    33005003397
20Prime!    15529255197
19221112275
18189798175
17Prime!    155155175
1686446865
1543223465
14177143
1383833
1266633
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 20
A250408

L base 10

L base 20

Next > 10^20
851058780133108785011814
84718748134318478171713
83718318952598138171713
82695175560655715961713
81695150546450515961713
80695150356530515961713
79673164237324613761713
78673164047404613761713
77673141570751413761713
76671827316137281761713
75671800871780081761713
7425336371173633521612
7325334013310433521612
721156294449265111511
711154889398845111511
701154827772845111511
691154821612845111511
681152381818325111511
671129896869892111511
661129838483892111511
651127392529372111511
641127334143372111511
631127330903372111511
62967573333757691411
61965440000445691411
60928622002268291411
59863563003653681411
58828857007588281411
57828680660868281411
56761853113581671411
55761600000061671411
54726970770796271411
53726911551196271411
52726786116876271411
51722790110972271411
50688570770758861411
49688511551158861411
48688386116838861411
47622960440692261411
46620898998980261411
45586676226766851411
44586617007166851411
43584560440654851411
42549854444589451411
41484799229974841411
40484730770374841411
39447783553877441411
38445844114485441411
37382836226382831411
36380720440270831411
35280959229590821411
34141026006201411411
33106143663416011411
32355746647553129
31355110011553129
30334843348433129
29334495594433129
281444884441108
27191919175
26Prime!    191719175
25191519175
24191319175
23178887175
22178687175
21178487175
203030354
192272254
182020254
171262154
161010154
15711743
14677643
13655643
1225232
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 21

L base 10

L base 21

Next > 10^20
105540226597117956220452015
104534791163223611974352015
103526951193663911596252015
102320566237227326650232015
101281307920220297031822015
10048893125212521398841915
9929693862121268396921914
9827451614050416154721914
9724074318272813470421914
9622425985636589524221914
958818666122166681881814
944783036055063038741814
93997030253520307991713
92926136044406316291713
91829934419144399281713
90Prime!    783577346437753871713
89491262581852621941713
88445067403047605441713
87398232526252328931713
86382754241424572831713
85370227940497220731713
84329248681868429231713
83285900524250095821713
82235303664663035321713
81138949504059498311713
80100914959594190011713
7986287883388782681613
7863885981189588361612
7761162924429261161612
7646906385583609641612
7523693247742396321612
7422774860068477221612
738819102120191881512
723387349094378331511
712899119591199821511
702350236263205321511
692173066866037121511
682074495459447021511
671281975157918211511
66906606776066091411
65591395445931951411
64272109889012721411
6388168171861881310
6225963292369521310
61440827728044129
60303880088303129
5998157575189119
5879375957397119
5766969496966119
5654482928445119
558087337808108
546801661086108
534672002764108
524475555744108
512130880312108
501696776961107
491418668141107
481378448731107
4790053500997
4662028202697
4549022209497
4442702072497
4342348432497
4240916190497
4134037304397
4029308039297
396893398686
386722227686
376698896686
364642246486
352835538286
342562265286
33661216676
32656365676
31623332676
30397979375
29373537375
28371017375
27237973275
26184448175
2584554865
2467227665
2320330265
228797854
216111654
2098933
19Prime!    75733
1850533
1748433
1624232
158822
146622
134422
122222
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 22

L base 10

L base 22

Next > 10^20
72743129965115699213472015
71726738116666118376272015
70724139717227179314272015
69720991514114151990272015
68716701869449681076172015
6772603022919220306271915
661509174422447190511813
651420540311304502411813
64958815692965188591713
63938954947494598391713
62908141478741418091713
61892332766672332981713
60890790444440970981713
59832180012100812381713
58751447576757441571713
57713609593959063171713
56192919528259192911713
55174671139311764711713
545741281418214751511
535738597479583751511
525674255955247651511
514951728682715941511
502766957275966721511
492324748884742321511
481454105350145411511
471003579797530011511
4619632323236911310
4513899242998311310
441162319132611139
4393648984639119
4277263836277119
4177185658177119
40Prime!    75293639257119
3918486568481118
381297007921107
371285665821107
3657559557597
3557523257597
3447218127497
3339908099397
3213372733197
315915519586
30510901575
29504840575
28296869275
27284648275
26240804275
25235953275
247909754
237656754
222838254
212585254
20577543
19566543
18555543
17544543
16533543
15Prime!    72733
1459533
1341432
1216132
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 23

L base 10

L base 23

Next > 10^20
7582106656979656601281914
7448165007898700561841914
7342834646313646438241914
724879178888887197841813
713062743666634726031813
70879475244425749781713
69811574375734751181713
68754271813181724571713
67301108385838011031713
668704516861540781511
658541617371614581511
647719588688591771511
637435643334653471511
627430675257603471511
615951759595715951511
605834001710043851511
595671102220117651511
584393219191239341511
572740782728704721511
561567767676776511511
551446455355464411511
541441487278414411511
53595681111865951411
5284635080536481310
511759179719571139
501724384834271139
491372149412731139
48881274472188129
47830493394038129
46676421124676129
45638980089836129
44625640046526129
43317227722713129
4263522022536118
4161029992016118
4046405150464118
393181771813107
382266116622107
3796558556997
3694996994997
3584363634897
3428256528297
3325404045297
3219975799197
31630703675
30583638575
29511611575
28464546475
27415151475
26345454375
25191119175
24104940175
238848854
228404854
216525654
204202454
19633643
18511543
17366343
16244243
15122143
1489833
1373733
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 24
A250409

L base 10

L base 24

Next > 10^20
103868125048558405218682015
102476209921661299026742015
101397638732222378367932015
100338476745005476748332015
9952199573010375991251914
988342917822871924381813
978308682755728680381813
967056739611693765071813
956898706466460789861813
945008072400427080051813
933515310999901351531813
923349357866875394331813
91562575119115752651713
90Prime!    378727823287278731713
8910816054450618011611
889788987878988791511
879749099299094791511
869723636963632791511
858938725552783981511
848938590509583981511
83Prime!    7266744544766271511
827206233433260271511
817092778087729071511
806684442224448661511
796494709790749461511
786494574747549461511
773798499999489731511
763520843634802531511
752964304840346921511
742948237673284921511
732790338383309721511
722735932223953721511
711089714741798011511
701063951215936011511
691003440104430011511
6852233595332251310
672084684864802139
662084226224802139
652024272724202139
641490461640941139
631318742478131139
621047699967401139
611042342432401139
60780089980087129
59686286682686129
58240745547042129
57129797797921129
56125825528521129
553032112303107
542315115132107
531516776151107
521039669301107
5198105018997
5086633366897
4976031306797
4872843482797
4749197919497
4645902095497
4541776771497
4435300035397
4331174711397
42Prime!    786568775
41765856775
40719291775
39713231775
38674747675
37628182675
36601410675
35583638575
34510301575
33492529475
32429692475
31402920475
30Prime!    367376375
29311811375
28276267275
27226762275
26220702275
25Prime!    185158175
2437447365
231363153
221262153
211101153
201000153
19855843
18699643
17622643
16466443
15233243
1457532
1352532
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 25
A250410

L base 10

L base 25

Next > 10^20
96776068037227308606772015
95625817722662277185262015
94Prime!    12727870161078727211913
93Prime!    12723987515789327211913
92Prime!    12723944979449327211913
9112628665767566826211913
9012626946434649626211913
8912626903898309626211913
88Prime!    12625852252258526211913
8712621969606969126211913
86Prime!    12621969535969126211913
8512529981525189925211913
8412529905353509925211913
8312528811171118825211913
826895600966900659861813
811099812644621899011813
80620052760672500261713
7982510187781015281612
7811341145541143111611
778581182628118581511
768542071317024581511
756599537773599561511
746069709190796061511
735077567076577051511
724046623132664041511
714046156565164041511
704007045254070041511
693093184348139031511
682597569196579521511
672558819991885521511
662558399299385521511
652519708680791521511
642067842824876021511
632062240404226021511
622028672927682021511
612023070507032021511
601566625252666511511
59899549559459981410
58893314004133981410
57619862772689161410
56280234884320821410
551678753578761139
54Prime!    1678699968761139
531678690968761139
5283895259838118
5183849694838118
5087486847897
4987438347897
4882777772897
4722345432296
468540045886
45949894975
44Prime!    949394975
43946764975
42946264975
41943634975
40943134975
39940504975
38Prime!    940004975
37898689875
36663936675
35663436675
34660806675
33660306675
32339793375
31Prime!    339293375
30336663375
29336163375
28333533375
27333033375
26330903375
25Prime!    330403375
24285958275
23282828275
2262662665
2162222665
20933943
19833843
18788743
17688643
16100143
1567633
1462633
1349432
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 26

L base 10

L base 26

Next > 10^20
90930281242222421820392015
8997672831787138276791914
8869960050353050069961914
8723346179121971643321913
8621623403303304326121913
8518977875686578779811913
8411390803808308093111913
8310565006595600565011913
827396087233278069371813
81951180767670811591712
80899732872782379981712
7936038307703830631611
7836035001100530631611
7735559778877955531611
7635556472274655531611
7513647851158746311611
7410093385583390011611
738897004740079881511
728892665656629881511
718732162726123781511
707387931013978371511
697222748684722271511
686125006560052161511
675207436263470251511
665123269796232151511
654205699499650241511
641798779097789711511
631060188688106011510
621034726862743011510
61924240660424291410
605404902094045139
595223922293225139
584726136316274139
574190117110914139
563693694963963139
553662197912663139
54Prime!    3610437340163139
533335051505333139
523193401043913139
513146469646413139
502183758573812139
492149753579412139
481181201021811139
471134269624311139
46185076670581128
4572728282727118
4430966666903118
436825225286107
424417777144107
412069559602107
4093324233997
3964309034697
3862626262697
3732113112397
36Prime!    31928291397
3523801083296
3421805081296
3313451543196
32982328975
31967976975
30828582875
29792429775
28653035675
27504840575
26463136475
25138783175
248434854
234919454
221898154
21Prime!    1747153
201484153
19Prime!    1333153
181070153
17900943
16822843
15744743
14411443
1398933
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 27
A250411

L base 10

L base 27

Next > 10^20
8433866944656449668331913
8330329608363806923031913
8229880463686364088921913
8129738829040928837921913
8028855669020966558821913
7928003544686445300821913
7820199239888932991021913
77Prime!    19757839797938757911913
7619059916535619950911913
7518009431292134900811913
7416536248949842635611913
739570011433411007591813
727520090744709002571813
714750847433474805741813
702958716488461785921813
69632403190913042361712
6837742733337247731611
6725338804408833521611
6612761490094167211611
659871153835117891511
649632176867123691511
638729516061592781511
628246854245864281511
615709849894890751511
606041548451406139
596014294924106139
585779540459775139
575193025203915139
565052248422505139
554806859586084139
544725972795274139
534520609060254139
524446399936444139
514280234320824139
503958336338593139
493817559557183139
482969036309692139
472904768674092139
462823881883282139
459058338509107
448417447148107
435364224635107
422487997842107
412132882312107
4083604063897
3960980890697
3821417141296
376716617686
36982728975
35946664975
34939293975
33873737875
32866366875
31757375775
30736863775
29663936675
28627872675
27554945575
26547574575
25438583475
24228782275
23119791175
226585654
211787153
201595153
191303153
18Prime!    1030153
17Prime!    91933
1683833
15Prime!    75733
1461632
1325232
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 28

L base 10

L base 28

Next > 10^20
80295187428778247815922014
79197996495665946997912014
7862428663252366824261913
7762154577494775451261913
7648756963565369657841913
7543800168676861008341913
7439619496090694916931913
7336010864757468010631913
7229883097515790388921913
7129184891616198481921913
7017470450848054074711913
693144350211205344131813
68202102350532012021712
6752499705507994251611
669183956965938191511
658501289398210581511
646295962426959261511
635487859395878451511
625254088288045251511
613191022622019131511
60541731441371451410
599693965693969139
588338331338338139
578332192912338139
566385093905836139
555788955598875139
544699722279964139
534120874780214139
52Prime!    3597871787953139
512636029206362139
50731212212137129
49396183381693129
48276220022672128
4789279097298118
4679124342197118
4513363136331117
4413240004231117
4311242524211117
4210549494501117
417298118927107
406175005716107
395760110675107
381538668351107
37Prime!    94714174997
3690417140997
35Prime!    77393937797
34Prime!    75158515797
3371175711797
3250059500597
3142777772496
3016104016196
291049940185
28Prime!    932423975
27878887875
26700300775
25660106675
24623132675
23569596575
22297279275
212080253
201696153
191525153
181040153
17633643
16577543
1569632
1446432
1323232
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 29

L base 10

L base 29

Next > 10^20
7496979977656779979691913
7385246862151268642581913
7283716248404842617381913
7183211042656240112381913
7065529203737302925561913
6964299560232065992461913
6844039980323089930441913
6736246098080890642631913
6633512971181179215331913
6518183088212880381811913
647608049299294080671813
63Prime!    116968092908696111711
6274239329923932471611
6152684690096486251611
6026587679976785621611
5912102077020121149
589852537352589139
578991895981998139
568939482849398139
558775005005778139
548511759571158139
538361888881638139
527696190916967139
51Prime!    7066183816607139
507040427240407139
496975552555796139
486127372737216139
475634774774365139
465060470740605139
454870236320784139
444240229220424139
434022056502204139
42Prime!    3957181817593139
413301418141033139
40Prime!    3000234320003139
392440776770442139
38Prime!    1145071705411139
3715865056851117
3615700600751117
3514914241941117
3414698289641117
3314533833541117
325983223895107
315255225525107
304771771774107
294043773404107
2869325239697
27991119975
26953735975
25852525875
24Prime!    795859775
23713931775
22707870775
21623332675
20617271675
19516061575
18465456475
17459395475
16358185375
151919153
14177143
13Prime!    92933
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 30

L base 10

L base 30

Next > 10^20
722131216899861213121812
712129370099007392121812
70126021958591206211711
695095666266659051510
684870351715307841510
672393180808139321510
662388925452988321510
6514313300331341149
64Prime!    1201117111021139
631201109011021139
6216004240061117
6115826462851117
6015599599551117
5915583138551117
5815347274351117
572134994312107
562127777212107
551142992411107
5463788873696
5329687869296
521743347185
51317871375
50316161375
49240204275
48229392275
47228582275
46227772275
45226962275
44210201275
43150105175
42139293175
41138483175
40Prime!    120102175
39Prime!    109290175
38108480175
3773553764
362060253
352030253
342000253
331979153
321949153
311919153
301898153
29Prime!    1060153
28Prime!    1030153
271000153
26711743
25600643
24522543
23444443
22411443
21333343
20300343
19255243
18222243
17177143
16144143
15111143
1486832
1343432
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 31

L base 10

L base 31

Next > 10^20
86203601295335921063022013
85114508475445748054112013
8495179041040140971591913
8394594846616648495491913
8292709922606229907291913
8184328141515141823481913
8080927343222343729081913
7980177025747520771081913
7878793716949617397871913
7768527011848110725861913
7655978727262727879551913
7540774872898278477041913
7434675009000900576431913
7327475309353903574721913
7218285212989212582811913
7112271454989454172211913
70422692422242962241712
69241917834387191421711
68237625580855267321711
67152945340435492511711
6699175280082571991611
6587447404404744781611
64Prime!    9610308580301691511
638312082028021381511
626733179497133761510
616351806160815361510
606161974747916161510
5919350999905391149
5818508300380581149
57Prime!    9115199915119139
569028337338209139
558760465640678139
548605751575068139
537707170717077139
527511392931157139
517225198915227139
507138336338317139
493406192916043139
4817039593071117
47Prime!    11819991811117
461551551551107
4596190916997
4484425244896
436520025686
426399993686
412390093285
401333333185
39915151975
38903030975
37Prime!    769696775
36757575775
35745454775
34638383675
33626262675
32614141675
31602020675
30468686475
29349494375
28337373375
27Prime!    325252375
26313131375
25301010375
248636854
234070454
222979254
212383253
202262253
192141253
182020253
17Prime!    1989153
161868153
15Prime!    1747153
14744743
13155143
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 32
A099165

L base 10

L base 32

Next > 10^20
120812984514664154892182014
119524139120660219314252014
118503857371331737583052014
117501939427227249391052014
116233980549779450893322013
11558883617333716388851913
11446501112585211105641913
11328089273242372980821913
11224490801292108094421913
1117760169122196106771812
1105712592177129521751812
1094657075711757075641812
1083307749455494770331812
1071124744433444742111812
106854919303039194581712
105333039357539303331711
104276305118115036721711
103274296432346924721711
102274021114111204721711
101Prime!    176247019107426711711
100170961718171690711711
99147779358539777411711
98131778850588771311711
97Prime!    131503532353051311711
96Prime!    108947113117498011711
95106039620269306011711
94104780157510874011711
93102638063608362011711
9234226692296622431611
9128699606606996821611
9022971582285179221611
8912787466664787211611
8810320780087023011610
8724916011061942149
8617438700783471149
8510641522514601149
848867028207688139
838842552552488139
828825076705288139
816886033306886139
805842794972485139
795806855586085139
784462757572644139
771462999992641139
761232143412321139
75935448844539128
74846261162648128
73691647746196128
72494889988494128
71444036630444128
70421833338124128
6934318181343117
6818884748881117
6714311211341117
6610269296201117
6510261916201117
648804774088107
636806006086107
623403003043107
612880990882107
601219669121107
5998376738996
5893390933996
5738891988396
563747747386
552980089285
542577775285
532149941285
522103301285
511825528185
50986768975
49980208975
48965856975
47840704875
46688288675
45667376675
44548784575
43542224575
42423632475
41382528375
40263936275
39125152175
3891221964
3780440864
3678008764
3571771764
3467227664
3360990664
3258558564
3156446564
3047777464
2936996364
285494554
273222353
262969253
252101253
24Prime!    1989153
231595153
22944943
21688643
20544543
19288243
18144143
1785832
1636332
159922
146622
133322
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 33

L base 10

L base 33

Next > 10^20
67382309112002119032832013
66375388983553898835732013
65194094024444204904912013
64187839544334459387812013
6394587212565212785491913
6266020415969514020661913
6147925193414391529741913
6037676937323739676731913
5934193149939941391431913
5830726109818901627031913
57498241857581428941711
56493988170718893941711
55439020615160209341711
54391909250529091931711
53262931124211392621711
52243611125211163421711
51224357127217534221711
50192557580857552911711
496813218781231861510
487087281827807139
475239168619325139
463298767678923139
453125102015213139
442957779777592139
432908060608092139
422736923296372139
4140909290904117
4030817071803117
3928681818682117
3812483938421117
3761078701696
362681186285
352621126285
341411114185
33901210975
32719291775
31654545675
30515351575
29450605475
28311411375
27236963275
26Prime!    182028175
25129492175
2442112464
2341551464
2240990464
213121353
202989253
192444253
181909153
171767153
161222153
151070153
1464632
1327232
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 34

L base 10

L base 34

Next > 10^20
73748508903223098058472013
72491160200220020611942013
71403296544884456923042013
70361205289669825021632013
69137388926116298837312013
68134649664994669464312013
6749803542000245308941913
6630682657898756286031913
65666185800085816661711
64663871325231783661711
63633445758575443361711
62627039920299307261711
61573605314135063751711
60519145914195419151711
59465711308031175641711
58428053215123508241711
57415967430347695141711
56299742378732479921711
55267122761672217621711
54117273276723727111711
53Prime!    113765454545673111711
5278941676676149871611
5161730611116037161611
5036304571175403631611
4930330807708033031611
4843649088094634149
479950190910599139
469326196916239139
455641401041465139
444048267628404139
4343590509534117
4235793239753117
4130632523603117
4030268686203117
3928185658182117
3822835253822117
3718319091381117
366447777446107
355086996805107
344601881064107
3352586852596
323150051385
312962269285
30863236875
29806660875
28744644775
27502020575
26296769275
253828353
243212353
233161353
222848253
212797253
202181253
19Prime!    1606153
18Prime!    1555153
17911943
16255243
1559532
1452532
133321
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 35

L base 10

L base 35

Next > 10^20
86808040509559050408082013
85769926787117876299672013
84765057562332657505672013
83480058958008598500842013
82263591762002671953622013
8177944037404730449771913
8077759131262131957771913
7977364569393965463771913
7876754595131595457671913
7774588190333091885471913
7673772397676793277371913
7573602199959991206371913
7470620448262844026071913
7363863835828538368361913
7261874328444823478161913
7121925485999584529121912
708407961199116970481812
698019497611679491081812
68949353582853539491711
67949128153518219491711
66945063627263605491711
65941540528250451491711
64Prime!    759308887888039571711
63751380567650831571711
62751138279728311571711
61565848148418485651711
60565281227221825651711
59561201752571021651711
58409169913199619041711
57405439933399345041711
56Prime!    379641601061469731711
55Prime!    375895068605985731711
54215486853586845121711
53211756873786571121711
52185716253526175811711
51177317137317137711711
50173020236320203711711
492321316961312321510
482170305050307121510
4730869533596803149
4628165944956182149
45Prime!    9710780870179139
449638309038369139
438703990993078139
422121358531212138
412102654562012138
4069497279496118
3956028182065117
3855972827955117
3755964546955117
3634145054143117
35Prime!    33842924833117
3433834643833117
3323780308732117
3223772027732117
3112599199521117
309166226619107
292692296285
28Prime!    188188175
276555654
266303654
254252453
243464353
232767253
222161253
211979153
201464153
191373153
18399343
17266243
16133143
1582832
1425232
133321
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011

Index Nr

Also palindromic
in base 36
A250412

L base 10

L base 36

Next > 10^20
98898117561881657118982013
97891287181001817821982013
96683327227337227233862013
95406850607447060586042013
94217837188228817387122013
9350564223595322465051913
9224765075909570567421912
918544041855814044581812
908392561866816529381812
891169798066089796111811
88773051714171503771711
87707018033308107071711
86706498676768946071711
85705461802081645071711
84669346184816439661711
83576735101015376751711
82508136249426318051711
81465249374739425641711
80464212500052124641711
79139068150518609311711
7858049861168940851611
773890040004009831510
763614008480041631510
753432014541023431510
7485582866828558149
7367743488434776149
7232866755766823149
7128420977902482149
7025120399302152149
693955010105593139
682402398932042138
671679755579761138
6673533033537117
6571904040917117
6466516061566117
6366394149366117
6261664946616117
6159552225595117
6056276967265117
5956102620165117
5854647974645117
5749931613994117
5644596069544117
5537579097573117
5437280408273117
5327958485972117
5222446164422117
5195234325996
504865568485
491006600185
48948884975
47924242975
46695059675
45691819675
44592729575
43518281575
42430603475
41Prime!    331513375
40186768175
39130103174
3898778964
3774114764
3615995164
354222453
343797353
333606353
323343353
31Prime!    3080353
302111253
291949153
281686153
271232153
26511543
25288243
24144143
23122142
2299932
2188832
2077732
1966632
1855532
1744432
1633332
1522232
1411132
133321
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011








MISSING TABLES PLANNED FOR
CONSTRUCTION IN THE FUTURE

Index Nr

Also palindromic
in base 60
A262069

L base 10

L base 60

Next >10^20
88192606056336506062912011
87191091392332931901912011
86191083060110603801912011
85129539493003949359212011
8410595114939411595011911
8310088602101206880011911
821117050288205071111810
81967916471746197691710
80948556612166558491710
79948127566657218491710
78908200113110028091710
77867560277720657681710
76846868958598686481710
75786988275728896871710
74706328655568236071710
73625761366631675261710
72444543500053454441710
71404485670765844041710
70263348503058433621710
69182781214121872811710
68182352168612532811710
676140607337060416169
665979490660949795169
654056041771406504169
644041670880761404169
632114962552694112169
622114927447294112169
611997507557057991169
601982186226812891169
591927217227127291169
581912846336482191169
571021449441201137
56872376673278127
55872322223278127
542230660322106
531486446841106
5260836380695
5160727270695
5060618160695
4960509050695
4860307030695
4758961698595
4658852588595
4558743478595
4458634368595
4358525258595
4258416148595
4145192915495
4045083805495
39Prime!    30196910395
3815550555195
3715534355195
3615441445195
35Prime!    15425245195
34Prime!    15332335195
3315316135195
3215223225195
3115207025195
3015114115195
2915005005195
282893398285
272623326285
261403304185
251116611184
24837273874
23279697274
2214884163
2111331163
205737553
195707553
185575553
175545553
165515553
155521
144421
133321
122221
11Prime!    1121
10911
9811
8Prime!    711
7611
6Prime!    511
5411
4Prime!    311
3Prime!    211
2111
1011













led Base 2 led Messages led

Palindromes in bases 2 and 10.
The main source for this table comes from the following weblink.
Binary/Decimal Palindromes by Charlton Harrison (email) from Austin, Texas.
See also Sloane's sequences A007632 and A046472.

" I just finished writing a distributed client/server program for finding these numbers, and I currently
have it running on 4 different machines at the same time and I'm finding them A LOT faster. That's how
I was able to come up with those new ones. I'd say there are more to come in the near future, too."

[ December 1, 2001 ]
Charlton Harrison once found this record binarydecimal palindrome
110 0010111100 0010101010 1101000011 1010000010
0000101110 0001011010 1010100001 1110100011

7475703079870789703075747
The binary string contains 83 digits !


[ April 11, 2003 ]
Dw (email) wrote me the following :

"Using a backtracking solver, I have found larger numbers.
The first of these, which is the next after the one mentioned above, is
50824513851188115831542805 (86 bit, 3*5*11*11*17*17*83*11974799*97488286319).
There are no other 86 bit double palindromes.

I also have found two 89 bit double palindromes, but I am not sure if they
are the next ones. There may be some lower ones in 89 bit (haven't searched
that space completely yet) or in 87 bit that I haven't found.
These numbers are
532079161251434152161970235 (5*29*85839676103*42748430836381)
and
552963956270141072659369255 (5*7*7*71*441607*71984077228507867)
As can be seen by their factor representation, they are all composite."


50824513851188115831542805 {26}
10101000001010100000100110101010101001100000000110010101010101100100000101010000010101 {86}

532079161251434152161970235 {27}
11011100000100000001001010010000011001110101010101110011000001001010010000000100000111011 {89}

552963956270141072659369255 {27}
11100100101100110101011000010001001111100100100100111110010001000011010101100110100100111 {89}


[ April 13, 2003 ]
Dw (email) found four new ones including the 6th double palindromic prime :

"They are, in opposite sorted order:
138758321383797383123857831 (87 bit, composite, the only 87 bit double palindrome)
390714505091666190505417093 (89 bit, prime)
351095331428353824133590153 (89 bit, composite)
795280629691202196926082597 (90 bit, composite, not sure if this is the next one)."

When asking Dw for an explanation or description in a few words
what he meant by 'Using a backtracking solver' he replied :

"A backtracking solver is one that solves a problem made up of smaller
problems by trying every one except if it knows its earlier guesses make all
later ones depending on them impossible.

For instance, if you're in a maze and know that all corridors with green
walls eventually lead to a dead end, you can turn around as soon as you find
such a wall (backtrack) if you're trying to find the exit.

The smaller problem is avoiding a dead end, and the larger one is
finding the exit.

If you want the details:

My general strategy goes that to find a double palindromic number, the
solution to its palindromic decimal representation minus its binary
representation must be zero (since they are equal).

Furthermore, you can write a decimal palindrome like 101 * a + 10 * b, where
a and b are digits. The same can be done for binary, and you end up with a
giant (linear diophantine) equation of positive decimal and negative binary factors.

The factors can then be solved, one at a time, using the extended euclidean
algorithm. These are the smaller problems.

I also have a table of maximum and minimum values for each step. That way, if
it's impossible for the binary factors left to subtract enough from the
decimal factors to get zero (or the other way around), the solver backtracks."

[ April 13, 2003 ]
Dw once found this record binarydecimal palindrome
1010010001 1101011100 1110010101 0010100001 0100000010 1000010100 1010100111 0011101011 1000100101
795280629691202196926082597
The binary string contains 90 digits !
The decimal string contains 27 digits !


138758321383797383123857831 {27}
111001011000111001101111010110010111011100111001110111010011010111101100111000110100111 {87}

351095331428353824133590153 {27}
10010001001101011010101000000110111100000100000100000111101100000010101011010110010001001 {89}

390714505091666190505417093 {27}
10100001100110001000000111100001100011000111011100011000110000111100000010001100110000101 {89}

795280629691202196926082597 {27}
101001000111010111001110010101001010000101000000101000010100101010011100111010111000100101 {90}


[ May 21, 2003 ]
Dw (email) found a new Binary/Decimal Palindrome :

"I have been trying to find a polynomial time (growth of time needed is a
polynomial of number of bits) algorithm for finding double palindromes of
base 2 and 10. I haven't succeeded yet (my backtracking solver being
exponential), but I have found some interesting things.

For one, to find double palindromes in base 2 and 8 is very simple. Each base 8
digit maps to three bits. Therefore, every double palindrome must consist
of digits who themselves are double palindromes.

For instance, 757 as well as 575 is double palindromic. (These values are 495
and 381 in decimal respectively).
5 maps to 101 in binary, and 7 to 111 in binary.

I have found 1609061098335005338901609061 (91 bits composite),
and this is the only 91 bit one. No 92 bit double palindrome exists, and
93 bits seems to require several days of searching; therefore I'm trying to
find a polynomial time algorithm as mentioned above.

Another approach could be to create a networked version (to do the search on
multiple computers), but I haven't done that yet."

[ May 21, 2003 ]
Dw once found this record binarydecimal palindrome
1 0100110010 1111101111 1100001110 1100100000
0010001000 0000100110 1110000111 1110111110 1001100101

1609061098335005338901609061
The binary palindrome contains 91 digits !
The decimal string contains 28 digits !

1609061098335005338901609061 {28}
1010011001011111011111100001110110010000000100010000000100110111000011111101111101001100101 {91}


[ June 12, 2003 ]
Dw (email) found new Binary/Decimal Palindromes :

"I rewrote my program to use another strategy at finding the numbers, and this
let me search somewhat faster. As a result, I have found binary/decimal
palindromes up to 102 bits -- broke the 100 bit barrier so to speak.

These are:

None at 92 or 93 bits.
17869806142184248124160896871 (94 bits)
19756291244127372144219265791 (94 bits)
30000258151173237115185200003 (95 bits)
30658464822225352222846485603 (95 bits)
56532345659072227095654323565 (96 bits)
None at 97 or 98 bits.
378059787464677776464787950873 (99 bits)
1115792035060833380605302975111 (100 bits)
None at 101 bits.
3390741646331381831336461470933 (102 bits)

There may be higher ones at 102 bits; I haven't completed the search there."


17869806142184248124160896871 {29}
1110011011110110001110101001000001000000000011001100000000001000001001010111000110111101100111 {94}

19756291244127372144219265791 {29}
1111111101011000000101011001100101101101100001111000011011011010011001101010000001101011111111 {94}

30000258151173237115185200003 {29}
11000001110111110100001110001010010000110100011011000101100001001010001110000101111101110000011 {95}

30658464822225352222846485603 {29}
11000110001000000010110011101000100010000101111111110100001000100010111001101000000010001100011 {95}

56532345659072227095654323565 {29}
101101101010101001110101110101101111011010100000000001010110111101101011101011100101010101101101 {96}

378059787464677776464787950873 {30}
100110001011001001110111010000000001110111000111010111000111011100000000010111011100100110100011001 {99}

1115792035060833380605302975111 {31}
1110000101010101000110001001111111101011111110110110110111111101011111111001000110001010101010000111 {100}

3390741646331381831336461470933 {31}
101010110011000001001111000000100001000111101001011110100101111000100001000000111100100000110011010101 {102}


[ June 17, 2003 ]
Dw (email) adds :

" There are no numbers for 103 bits."
[ Note : In fact there is one! See index number 97. PDG ]

[ June 17, 2003 ]
Dw once found this record binarydecimal palindrome
10 1010110011 0000010011 1100000010 0001000111 1010010111
1
010010111 1000100001 0000001111 0010000011 0011010101

3390741646331381831336461470933
The binary palindrome contains 102 digits !
The decimal string contains 31 digits !

blue Binary/Decimal Palindromes by Charlton Harrison (email) : the longest list in existence ?


[ September 30, 2015 ]
Three more stunning numbers could be retrieved from Sloane's OEIS database.
See index numbers 124, 125 & 126.

[ September 30, 2015 ]
A former record binarydecimal palindrome
100110011011011101000001000010000011000111001011100111100011101000
00101110001111001110100111000110000010000100000101110110110011001

1634587141488515712882175158841417854361
The binary palindrome contains 131 digits !
The decimal string contains 40 digits !


[ March 8, 2020 ]
Many more numbers could be retrieved from Sloane's OEIS database.
See index numbers up to 147. The record dates from the end of 2015.

[ December 30, 2015 ]
The current record binarydecimal palindrome
Search team : Robert G. Wilson v, Charlton Harrison, Ilya Nikulshin & Andrey Astrelin
11010001010011101000000001001100010000000010110001011110100100101011100110101
0101100111010100100101111010001101000000001000110010000000010111001010001011

9335388324586156026843333486206516854238835339
The binary palindrome contains 153 digits !
The decimal string contains 46 digits !













Sources Revealed

blue Binary/Decimal Palindromes by Charlton Harrison (email) : the longest list in existence ?

Neil Sloane's "Integer Sequences" Encyclopedia can be consulted online :
Neil Sloane's Integer Sequences

I sampled the following base X palindromic numbers sequences from the table :

%N Binary expansion is palindromic. under A006995 -- Sum of digits A043261
%N Palindromes in base 3 (written in base 10). under A014190 -- Sum of digits A043262
%N Palindromes in base 4 (written in base 10). under A014192 -- Sum of digits A043263
%N Palindromic in base 5. under A029952 -- Sum of digits A043264
%N Palindromic in base 6. under A029953 -- Sum of digits A043265
%N Palindromic in base 7. under A029954 -- Sum of digits A043266
%N Palindromic in base 8. under A029803 -- Sum of digits A043267
%N Palindromic in base 9. under A029955 -- Sum of digits A043268
%N Palindromes. under A002113 -- Sum of digits A043269
%N Palindromic in base 11. under A029956 -- Sum of digits A043270
%N Palindromic in base 12. under A029957 -- Sum of digits A043271
%N Palindromic in base 13. under A029958 -- Sum of digits A043272
%N Palindromic in base 14. under A029959 -- Sum of digits A043273
%N Palindromic in base 15. under A029960 -- Sum of digits A043274
%N Palindromic in base 16. under A029730 -- Sum of digits A043275

%N Palindromic in bases 2 and 3. under A060792.
%N Palindromic in bases 2 and 10. under A007632.
%N Palindromic in bases 3 and 10. under A007633.
%N Palindromic in bases 4 and 10. under A029961.
%N Palindromic in bases 5 and 10. under A029962.
%N Palindromic in bases 6 and 10. under A029963.
%N Palindromic in bases 7 and 10. under A029964.
%N Palindromic in base 8 and base 10. under A029804.
%N Palindromic in bases 9 and 10. under A029965.
%N Palindromic in bases 11 and 10. under A029966.
%N Palindromic in bases 12 and 10. under A029967.
%N Palindromic in bases 13 and 10. under A029968.
%N Palindromic in bases 14 and 10. under A029969.
%N Palindromic in bases 15 and 10. under A029970.

%N Square in base 2 is a palindrome. under A003166.
%N Squares which are palindromes in base 2. under A029983.
%N n^2 is palindromic in base 3. under A029984.
%N Squares which are palindromic in base 3. under A029985.
%N n^2 is palindromic in base 4. under A029986.
%N Squares which are palindromic in base 4. under A029987.
%N n^2 is palindromic in base 5. under A029988.
%N Squares which are palindromic in base 5. under A029989.
%N n^2 is palindromic in base 6. under A029990.
%N Squares which are palindromic in base 6. under A029991.
%N n^2 is palindromic in base 7. under A029992.
%N Squares which are palindromic in base 7. under A029993.
%N n^2 is palindromic in base 8. under A029805.
%N n in base 8 is a palindromic square. under A029806.
%N n^2 is palindromic in base 9. under A029994.
%N Squares which are palindromic in base 9. under A029995.
%N Square is a palindrome. under A002778.
%N Palindromic Squares. under A002779.
%N n^2 is palindromic in base 11. under A029996.
%N Squares which are palindromic in base 11. under A029997.
%N n^2 is palindromic in base 12. under A029737.
%N Squares which are palindromic in base 12. under A029738.
%N n^2 is palindromic in base 13. under A029998.
%N Squares which are palindromic in base 13. under A029999.
%N n^2 is palindromic in base 14. under A030072.
%N Squares which are palindromes in base 14. under A030074.
%N n^2 is palindromic in base 15. under A030073.
%N Squares which are palindromes in base 15. under A030075.
%N n^2 is palindromic in base 16. under A029733.
%N Palindromic squares in base 16. under A029734.

%N n^3 is palindromic in base 4. under A046231.
%N Cubes which are palindromes in base 4. under A046232.
%N n^3 is palindromic in base 5. under A046233.
%N Cubes which are palindromes in base 5. under A046234.
%N n^3 is palindromic in base 6. under A046235.
%N Cubes which are palindromes in base 6. under A046236.
%N n^3 is palindromic in base 7. under A046237.
%N Cubes which are palindromes in base 7. under A046238.
%N n^3 is palindromic in base 8. under A046239.
%N Cubes which are palindromes in base 8. under A046240.
%N n^3 is palindromic in base 9. under A046241.
%N Cubes which are palindromes in base 9. under A046242.
%N Cube is a palindrome. under A002780.
%N Palindromic cubes. under A002781.
%N n^3 is palindromic in base 11. under A046243.
%N Cubes which are palindromes in base 11. under A046244.
%N n^3 is palindromic in base 12. under A046245.
%N Cubes which are palindromes in base 12. under A046246.
%N n^3 is palindromic in base 13. under A046247.
%N Cubes which are palindromes in base 13. under A046248.
%N n^3 is palindromic in base 14. under A046249.
%N Cubes which are palindromes in base 14. under A046250.
%N n^3 is palindromic in base 15. under A046251.
%N Cubes which are palindromes in base 15. under A046252.
%N n^3 is palindromic in base 16. under A029735.
%N Cubes which are palindromes in base 16. under A029736.

%N Palindromic primes in base 2. under A016041.
%N Palindromic primes in base 3. under A029971.
%N Palindromic primes in base 4. under A029972.
%N Palindromic primes in base 5. under A029973.
%N Palindromic primes in base 6. under A029974.
%N Palindromic primes in base 7. under A029975.
%N Palindromic primes in base 8. under A029976.
%N Octal palindromes which are also primes. under A006341.
%N Palindromic primes in base 9. under A029977.
%N Palindromic primes. under A002385.
%N Palindromic primes in base 11. under A029978.
%N Palindromic primes in base 12. under A029979.
%N Palindromic primes in base 13. under A029980.
%N Palindromic primes in base 14. under A029981.
%N Palindromic primes in base 15. under A029982.
%N Palindromic primes in base 16. under A029732.

%N Palindromic primes in base 10 and base 2. under A046472.
%N Palindromic primes in base 10 and base 3. under A046473.
%N Palindromic primes in base 10 and base 4. under A046474.
%N Palindromic primes in base 10 and base 6. under A046475.
%N Palindromic primes in base 10 and base 7. under A046476.
%N Palindromic primes in base 10 and base 8. under A046477.
%N Palindromic primes in base 10 and base 9. under A046478.
%N Palindromic primes. under A002385.
%N Palindromic primes in base 10 and base 11. under A046479.
%N Palindromic primes in base 10 and base 12. under A046480.
%N Palindromic primes in base 10 and base 13. under A046481.
%N Palindromic primes in base 10 and base 14. under A046482.
%N Palindromic primes in base 10 and base 15. under A046483.
%N Palindromic primes in base 10 and base 16. under A046484.

%N Palindromic primes in bases 2 and 4. under A056130.
%N Palindromic primes in bases 2 and 8. under A056145.
%N Palindromic primes in bases 4 and 8. under A056146.

%N Not palindromic in any base from 2 to n-2. under A016038.
%N Smallest palindrome greater than n in bases n and n+1. under A048268.
%N First palindrome greater than n+2 in bases n+2 and n. under A048269.
%N The first non-trivial (k>n+2) palindromic prime in both bases n and n+2. under A057199.
%N Symmetric bit strings (bit-reverse palindromes),
including as many leading as trailing zeros. under A057890.

Click here to view some of the author's [P. De Geest] entries to the table.
Click here to view some entries to the table about palindromes.


More Integer Sequences from Sloane's OEIS database



  1. A043001 n-th base 3 palindrome that starts with 1. - Clark Kimberling
  2. A043002 n-th base 3 palindrome that starts with 2. - Clark Kimberling
  3. A043003 n-th base 4 palindrome that starts with 1. - Clark Kimberling
  4. A043004 n-th base 4 palindrome that starts with 2. - Clark Kimberling
  5. A043005 n-th base 4 palindrome that starts with 3. - Clark Kimberling
  6. A043006 n-th base 5 palindrome that starts with 1. - Clark Kimberling
  7. A043007 n-th base 5 palindrome that starts with 2. - Clark Kimberling
  8. A043008 n-th base 5 palindrome that starts with 3. - Clark Kimberling
  9. A043009 n-th base 5 palindrome that starts with 4. - Clark Kimberling
  10. A043010 n-th base 6 palindrome that starts with 1. - Clark Kimberling
  11. A043011 n-th base 6 palindrome that starts with 2. - Clark Kimberling
  12. A043012 n-th base 6 palindrome that starts with 3. - Clark Kimberling
  13. A043013 n-th base 6 palindrome that starts with 4. - Clark Kimberling
  14. A043014 n-th base 6 palindrome that starts with 5. - Clark Kimberling
  15. A043015 n-th base 7 palindrome that starts with 1. - Clark Kimberling
  16. A043016 n-th base 7 palindrome that starts with 2. - Clark Kimberling
  17. A043017 n-th base 7 palindrome that starts with 3. - Clark Kimberling
  18. A043018 n-th base 7 palindrome that starts with 4. - Clark Kimberling
  19. A043019 n-th base 7 palindrome that starts with 5. - Clark Kimberling
  20. A043020 n-th base 7 palindrome that starts with 6. - Clark Kimberling
  21. A043021 n-th base 8 palindrome that starts with 1. - Clark Kimberling
  22. A043022 n-th base 8 palindrome that starts with 2. - Clark Kimberling
  23. A043023 n-th base 8 palindrome that starts with 3. - Clark Kimberling
  24. A043024 n-th base 8 palindrome that starts with 4. - Clark Kimberling
  25. A043025 n-th base 8 palindrome that starts with 5. - Clark Kimberling
  26. A043026 n-th base 8 palindrome that starts with 6. - Clark Kimberling
  27. A043027 n-th base 8 palindrome that starts with 7. - Clark Kimberling
  28. A043028 n-th base 9 palindrome that starts with 1. - Clark Kimberling
  29. A043029 n-th base 9 palindrome that starts with 2. - Clark Kimberling
  30. A043030 n-th base 9 palindrome that starts with 3. - Clark Kimberling
  31. A043031 n-th base 9 palindrome that starts with 4. - Clark Kimberling
  32. A043032 n-th base 9 palindrome that starts with 5. - Clark Kimberling
  33. A043033 n-th base 9 palindrome that starts with 6. - Clark Kimberling
  34. A043034 n-th base 9 palindrome that starts with 7. - Clark Kimberling
  35. A043035 n-th base 9 palindrome that starts with 8. - Clark Kimberling
  36. A043036 n-th base 10 palindrome that starts with 1. - Clark Kimberling
  37. A043037 n-th base 10 palindrome that starts with 2. - Clark Kimberling
  38. A043038 n-th base 10 palindrome that starts with 3. - Clark Kimberling
  39. A043039 n-th base 10 palindrome that starts with 4. - Clark Kimberling
  40. A043040 n-th base 10 palindrome that starts with 5. - Clark Kimberling
  41. A043041 n-th base 10 palindrome that starts with 6. - Clark Kimberling
  42. A043042 n-th base 10 palindrome that starts with 7. - Clark Kimberling
  43. A043043 n-th base 10 palindrome that starts with 8. - Clark Kimberling
  44. A043044 n-th base 10 palindrome that starts with 9. - Clark Kimberling


  1. A043045 a(n)=(s(n)+2)/3, where s(n)=n-th base 3 palindrome that starts with 1. - Clark Kimberling
  2. A043046 a(n)=(s(n)+1)/3, where s(n)=n-th base 3 palindrome that starts with 2. - Clark Kimberling
  3. A043047 a(n)=(s(n)+3)/4, where s(n)=n-th base 4 palindrome that starts with 1. - Clark Kimberling
  4. A043048 a(n)=(s(n)+2)/4, where s(n)=n-th base 4 palindrome that starts with 2. - Clark Kimberling
  5. A043049 a(n)=(s(n)+1)/4, where s(n)=n-th base 4 palindrome that starts with 3. - Clark Kimberling
  6. A043050 a(n)=(s(n)+4)/5, where s(n)=n-th base 5 palindrome that starts with 1. - Clark Kimberling
  7. A043051 a(n)=(s(n)+3)/5, where s(n)=n-th base 5 palindrome that starts with 2. - Clark Kimberling
  8. A043052 a(n)=(s(n)+2)/5, where s(n)=n-th base 5 palindrome that starts with 3. - Clark Kimberling
  9. A043053 a(n)=(s(n)+1)/5, where s(n)=n-th base 5 palindrome that starts with 4. - Clark Kimberling
  10. A043054 a(n)=(s(n)+5)/6, where s(n)=n-th base 6 palindrome that starts with 1. - Clark Kimberling
  11. A043055 a(n)=(s(n)+4)/6, where s(n)=n-th base 6 palindrome that starts with 2. - Clark Kimberling
  12. A043056 a(n)=(s(n)+3)/6, where s(n)=n-th base 6 palindrome that starts with 3. - Clark Kimberling
  13. A043057 a(n)=(s(n)+2)/6, where s(n)=n-th base 6 palindrome that starts with 4. - Clark Kimberling
  14. A043058 a(n)=(s(n)+1)/6, where s(n)=n-th base 6 palindrome that starts with 5. - Clark Kimberling
  15. A043059 a(n)=(s(n)+6)/7, where s(n)=n-th base 7 palindrome that starts with 1. - Clark Kimberling
  16. A043060 a(n)=(s(n)+5)/7, where s(n)=n-th base 7 palindrome that starts with 2. - Clark Kimberling
  17. A043061 a(n)=(s(n)+4)/7, where s(n)=n-th base 7 palindrome that starts with 3. - Clark Kimberling
  18. A043062 a(n)=(s(n)+3)/7, where s(n)=n-th base 7 palindrome that starts with 4. - Clark Kimberling
  19. A043063 a(n)=(s(n)+2)/7, where s(n)=n-th base 7 palindrome that starts with 5. - Clark Kimberling
  20. A043064 a(n)=(s(n)+1)/7, where s(n)=n-th base 7 palindrome that starts with 6. - Clark Kimberling
  21. A043065 a(n)=(s(n)+7)/8, where s(n)=n-th base 8 palindrome that starts with 1. - Clark Kimberling
  22. A043066 a(n)=(s(n)+6)/8, where s(n)=n-th base 8 palindrome that starts with 2. - Clark Kimberling
  23. A043067 a(n)=(s(n)+5)/8, where s(n)=n-th base 8 palindrome that starts with 3. - Clark Kimberling
  24. A043068 a(n)=(s(n)+4)/8, where s(n)=n-th base 8 palindrome that starts with 4. - Clark Kimberling
  25. A043069 a(n)=(s(n)+3)/8, where s(n)=n-th base 8 palindrome that starts with 5. - Clark Kimberling
  26. A043070 a(n)=(s(n)+2)/8, where s(n)=n-th base 8 palindrome that starts with 6. - Clark Kimberling
  27. A043071 a(n)=(s(n)+1)/8, where s(n)=n-th base 8 palindrome that starts with 7. - Clark Kimberling
  28. A043072 a(n)=(s(n)+8)/9, where s(n)=n-th base 9 palindrome that starts with 1. - Clark Kimberling
  29. A043073 a(n)=(s(n)+7)/9, where s(n)=n-th base 9 palindrome that starts with 2. - Clark Kimberling
  30. A043074 a(n)=(s(n)+6)/9, where s(n)=n-th base 9 palindrome that starts with 3. - Clark Kimberling
  31. A043075 a(n)=(s(n)+5)/9, where s(n)=n-th base 9 palindrome that starts with 4. - Clark Kimberling
  32. A043076 a(n)=(s(n)+4)/9, where s(n)=n-th base 9 palindrome that starts with 5. - Clark Kimberling
  33. A043077 a(n)=(s(n)+3)/9, where s(n)=n-th base 9 palindrome that starts with 6. - Clark Kimberling
  34. A043078 a(n)=(s(n)+2)/9, where s(n)=n-th base 9 palindrome that starts with 7. - Clark Kimberling
  35. A043079 a(n)=(s(n)+1)/9, where s(n)=n-th base 9 palindrome that starts with 8. - Clark Kimberling
  36. A043080 a(n)=(s(n)+9)/10, where s(n)=n-th base 10 palindrome that starts with 1. - Clark Kimberling
  37. A043081 a(n)=(s(n)+8)/10, where s(n)=n-th base 10 palindrome that starts with 2. - Clark Kimberling
  38. A043082 a(n)=(s(n)+7)/10, where s(n)=n-th base 10 palindrome that starts with 3. - Clark Kimberling
  39. A043083 a(n)=(s(n)+6)/10, where s(n)=n-th base 10 palindrome that starts with 4. - Clark Kimberling
  40. A043084 a(n)=(s(n)+5)/10, where s(n)=n-th base 10 palindrome that starts with 5. - Clark Kimberling
  41. A043085 a(n)=(s(n)+4)/10, where s(n)=n-th base 10 palindrome that starts with 6. - Clark Kimberling
  42. A043086 a(n)=(s(n)+3)/10, where s(n)=n-th base 10 palindrome that starts with 7. - Clark Kimberling
  43. A043087 a(n)=(s(n)+2)/10, where s(n)=n-th base 10 palindrome that starts with 8. - Clark Kimberling
  44. A043088 a(n)=(s(n)+1)/10, where s(n)=n-th base 10 palindrome that starts with 9. - Clark Kimberling


  1. A016038 Strictly non-palindromic numbers: n is not palindromic in any base b with 2 <= b <= n-2. - N. J. A. Sloane.
  2. A100563 Number of bases less than sqrt(n) in which n is a palindrome. - Gordon Robert Hamilton





Contributions

Kevin Brown informed me that he has more info about tetrahedral palindromes in other base representations.
Link to his article :
point On General Palindromic Numbers thumb up

Alain Bex (email) sent me the first palindromic squares in base 12 - go to topic.

Dw (email) found several binary/decimal palindromes of record lengths - go to topic.


Richard Gosiorovsky (email)
Also Palindromic in Base 16 (OEIS A029731)
[ do 7-8/3/2024 7:33 ]

Dear Mr. De Geest,

I would like to ask you for updating the table re. numbers that are palindromic in bases 10 and 16.
I did some progress on it, and found 51 new members of the sequence. See indices 84 up to 134.
Full list of new members is in the text file in the attachment.

Thank you,

Richard Gosiorovsky, Bratislava


When I asked Richard how he achieved his results he replied:

I was inspired by Eshed Schacham's nice article:
"Finding Binary & Decimal Palindromes"

The method is useful for powers of two bases (2,4,8,16).
For now I do not plan other bases. It took me 3 days of
experimenting (programming) and 2 days of running (CPU time).

If you are interested in I am sending you my piece of code
in C language (palindrom.c) with external function in assembler
allowing multiply two 64-bit integers into 128-bit value.

Now I must go on with my real job, programming of course :)

Richard
//
//   Looking for Numbers that are palindromic in bases 10 and 16 simultaneously
//

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

#define ull unsigned long long  // 64-bit integer

extern ull mul128(ull *c, ull a, ull b);  // mul128.asm, see here:

// mul128 PROC
// mov rax, rdx              ; rdx - 2nd argument,  r8 - 3rd argument
// mul r8                    ; multiply rax * r8 -> result = 128-bit rdx:rax
// mov qword ptr [rcx], rdx  ; rcx - 1st argument
// ret                       ; return rax    
// mul128 ENDP

inline ull reverse(ull x) { ull q, y=0;  while(x) { q=x/10;  y=10*(y-q)+x;  x=q; }  return y; }

inline int is_palind_128(ull h64, ull l64, int sh1, int sh2)
 {
   while(sh1 >= 0 ) { if ((h64>>sh1 & 0xf) != (l64>>sh2 & 0xf)) return 0;   sh1-=4;  sh2+=4; }  sh1 = 60;  
   while(sh1 > sh2) { if ((l64>>sh1 & 0xf) != (l64>>sh2 & 0xf)) return 0;   sh1-=4;  sh2+=4; }  // here we test only in lower 64-bit
   return 1;
 }

//           012345678901234567890
#define FROM 10000000000000LL
#define UPTO 100000000000000LL
#define M4   10000000000LL
#define M8   1000000
#define M12  100

int main(int argc, char *argv[])
 {
   int sh=-999, k=0;
   ull h64, l64;  // upper & lower 64-bit of palindrome

   for(ull i=FROM; i<UPTO; i++)  // i - half of palindrome
    {
      if (i%1000000000==0) printf(" %lld mld.   %d sec.  %16llx\r", i/1000000000, clock()/1000, h64);

      l64 = mul128(&h64, i/10, UPTO) + reverse(i);  // create palindrome:  i - for even symmetry,  i/10 - for odd symmetry

      if (sh==-999) { sh=60;   while((h64>>sh & 0xf)==0) sh-=4; }  // find initial shift for leading hex digit
      if (h64>>(sh+4) & 0xf) sh+=4;  // hex digit overflow happened -> increase shift

      if (i % M4 == 0) if ((h64 >>(sh   ) & 0x000f) != (l64 & 0x000f)) { i+=M4 -1;  continue; } // skip this foursome of decimal digits
      if (i % M8 == 0) if ((h64 >>(sh- 8) & 0x00f0) != (l64 & 0x00f0)) { i+=M8 -1;  continue; }
      if (i % M12== 0) if ((h64 >>(sh-16) & 0x0f00) != (l64 & 0x0f00)) { i+=M12-1;  continue; }

      // 3*4 - first/last 3 hex digits was already tested by 3 upper conditions
      if (is_palind_128(h64, l64, sh-3*4, 3*4)) printf(" %4d.  %lld  %8llx:%016llx  %d sec.\n", ++k, i, h64, l64, clock()/1000);
    }

   printf(" total time = %d sec.\t\t\t\n", clock()/1000);   getchar();
 }



Eshed Schacham's article can be found following this link:
https://ashdnazg.github.io/articles/22/Finding-Really-Big-Palindromes
As a software developer he also made public his .c code he wrote for this topic and explains the algorithm in great depth.

To my surprise he found 35 new decimal palindromes that are also palindromic in base 2 or binary.
I added them forthwith to my webpage. Please refer to indices 148 up to 183 in the very first
scrolltable of this very page. Impressive if you consider their record lengths.


Richard Gosiorovsky (email)
Dual-base Palindromes
[ do 2/5/2024 6:02 ]

Hi Patrick,

I am sending you in the attachment several
new records for dual-base palindromes:

base 10 & 3:    4 new records → From [71] to [74]
base 10 & 4:   35 new records → From [65] to [99]
base 10 & 5:  100 new records → From [84] to [183]
base 10 & 6:    9 new records → From [110] to [118]
base 10 & 7:    8 new records → From [74] to [81]
base 10 & 8:   43 new records → From [89] to [131]
base 10 & 9:    5 new records → From [71] to [75]
base 10 & 16:   9 new records → From [135] to [143]

Thank you for this interesting entertainment.

For bases 10 & 4, 10 & 8 and 10 & 16 I used practically the same method as I mentioned earlier.
For base pair 10 & 5 I used very similar method, main difference is that solutions don't fit into
128-bit (it prunes much faster) so I rewrite the code using GMP library (GNU multiple precision).

For the rest of base pairs I used optimized brute force method, where I generate all possible
palindromes in one base and check it in another one. In cases where one base is power of 2
it is pretty straightforward (just bits comparison).

In all cases (except 10 & 5) I employ possibility of Intel processor to multiply two 64-bit integers
into 128-bit value (rdx:rax) and division of this 128-bit value into quotient and remainder
(instructions mul, div).
Richard


Richard Gosiorovsky (email)
Dual-base Palindromes (bases 10 & 5)
[ do 5/8/2024 16:44 ]

Hi Patrick, Hi Eshed,

I am here again, I would like to ask you for updating dual-base
palindrome sequence A029962 (bases 10 & 5), where I found 52 new
members (in the attachement). I improved algorithm a bit, but it
is still far from optimal. Changing bases to 10 & 2 I can not
achieve Eshed's records at all. Basic idea remains the same.

Richard

PS: For better understanding I am sending the source code too
(it uses GMP - GNU multiple precision library)

/*
    Looking for numbers simultaneously palindromic in bases 10 and 5 
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

#include "gmp.h"

#define ODD 1   // 0 - even symmetry  1 - odd symmetry

#define N 24    
#define M (2*N-1)  // length of palindrome

mpz_t tmp, aux;
mpz_t D[128], P[128];  // pre-computed constants: D[i] = 10^i,  P[i] = 5^i
mpz_t e[128], h[128];  // e[] - end of palindrome,  h[] - beginning of palindrome

int d[128], m1, m2;  // 5^m = divisor for leading digit
char s[256], s1[256], s2[256];

int ispalind(char *s, int n) { for(int i=0; i<n/2; i++) if (s[i] != s[n-i-1]) return 0;  return 1; }

void init_m1(mpz_t x) { m1 = M;   do { m1++;  mpz_fdiv_q(aux, x, P[m1]); } while (mpz_cmp_ui(aux, 5) >= 0); }
void init_m2(mpz_t x) { m2 = M;   do { m2++;  mpz_fdiv_q(aux, x, P[m2]); } while (mpz_cmp_ui(aux, 5) >= 0); }

int get_digit1(mpz_t x, int i)  // get i-th leading digit of x in base 5
 {
   mpz_fdiv_q(aux, x, P[m1]); 

   if (mpz_cmp_ui(aux, 5) >=0) m1++; 
   if (mpz_cmp_ui(aux, 0) <=0) m1--; 

   mpz_fdiv_q(aux, x, P[m1-i]);
   return mpz_fdiv_ui(aux, 5);
 }

int get_digit2(mpz_t x, int i)  // get i-th leading digit of x in base 5
 {
   mpz_fdiv_q(aux, x, P[m2]); 

   if (mpz_cmp_ui(aux, 5) >=0) m2++; 
   if (mpz_cmp_ui(aux, 0) <=0) m2--; 

   mpz_fdiv_q(aux, x, P[m2-i]);
   return mpz_fdiv_ui(aux, 5);
 }

void recur(int w)
 {
   if (w==6) { for(int i=0; i<6; i++) printf("%d", d[i]);  printf("  %d\"\r", clock()/1000); }

   if (w==N) 
    {
      mpz_add(tmp, h[N-1], (ODD==0)?e[N-1]:e[N-2]);
      mpz_get_str(s, 5, tmp);
      if (ispalind(s, strlen(s))) 
       { 
         for(int i=0; i<N; i++) printf("%d", d[i]);  
         printf("  %d  %d sec.\n", ODD, clock()/1000); 
       }
      return;
    }

   for(d[w]=0; d[w]<=9; d[w]++)
    {
      mpz_mul_ui(tmp, D[w], d[w]);        mpz_add(e[w], e[w-1], tmp);
      mpz_mul_ui(tmp, D[M-w-ODD], d[w]);  mpz_add(h[w], h[w-1], tmp);

      mpz_fdiv_q(tmp, e[w], P[w]);
      int f = mpz_fdiv_ui(tmp, 5); 
                                      
      mpz_add(tmp, h[w], D[M-w-ODD]); 

      if (f==get_digit1(h[w], w) || f==get_digit2(tmp, w)) recur(w+1);
    }
 }

int main()
 {
   printf("\n N = %d   ODD = %d\n\n", N, ODD);

   mpz_init(tmp);   mpz_init(aux); 
   for(int i=1; i<128; i++) { mpz_init(D[i]);  mpz_init(P[i]);  mpz_init(e[i]);  mpz_init(h[i]); }

   mpz_set_ui(D[0], 1);   for(int i=1; i<128; i++) mpz_mul_ui(D[i], D[i-1], 10); 
   mpz_set_ui(P[0], 1);   for(int i=1; i<128; i++) mpz_mul_ui(P[i], P[i-1], 5); 

   for(d[0]=1; d[0]<=9; d[0]++)
    {
      mpz_set_ui(e[0], d[0]);  
      mpz_mul_ui(h[0], D[M-ODD], d[0]); 

      int f = mpz_fdiv_ui(e[0], 5); 
                                    
      mpz_add(tmp, h[0], D[M-ODD]); 

      init_m1(h[0]); 
      init_m2(tmp);

      if (f==get_digit1(h[0], 0) || f==get_digit2(tmp, 0)) recur(1);
    }

   printf(" total time = %d sec.\t\t\t\n", clock()/1000); 
   getchar();
 }













 

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