number.wiki

Term

Palindrome

Numbers whose decimal digits read the same forwards and backwards.

203 numbers tagged.

A palindromic number reads the same forwards and backwards in its decimal representation. Examples: 11, 121, 1234321, 9999999.

The definition is base-dependent: 9 (decimal palindrome) is also 1001 in base 2 — a binary palindrome. Some numbers are palindromes in multiple bases simultaneously.

A famous open problem is the Lychrel conjecture: starting from any number, repeatedly add the number to its digit-reversal. For most numbers, you eventually reach a palindrome. The number 196 is the smallest candidate that has not yet been shown to either reach a palindrome or to never reach one — it has been iterated billions of times without producing a palindrome.

11 22 33 44 55 66 77 88 99 101 111 121 131 141 151 161 171 181 191 202 212 222 232 242 252 262 272 282 292 303 313 323 333 343 353 363 373 383 393 404 414 424 434 444 454 464 474 484 494 505 515 525 535 545 555 565 575 585 595 606 616 626 636 646 656 666 676 686 696 707 717 727 737 747 757 767 777 787 797 808 818 828 838 848 858 868 878 888 898 909 919 929 939 949 959 969 979 989 999 1,001 1,111 1,221 1,331 1,441 1,551 1,661 1,771 1,881 1,991 2,002 10,301 10,501 10,601 11,311 11,411 12,421 12,721 12,821 13,331 13,831 13,931 14,341 14,741 15,451 15,551 16,061 16,361 16,561 16,661 17,471 17,971 18,181 18,481 19,391 19,891 19,991 30,103 30,203 30,403 30,703 30,803 31,013 31,513 32,323 32,423 33,533 34,543 34,843 35,053 35,153 35,353 35,753 36,263 36,563 37,273 37,573 38,083 38,183 38,783 39,293 70,207 70,507 70,607 71,317 71,917 72,227 72,727 73,037 73,237 73,637 74,047 74,747 75,557 76,367 76,667 77,377 77,477 77,977 78,487 78,787 78,887 79,397 79,697 79,997 90,709 91,019 93,139 93,239 93,739 94,049 94,349 94,649 94,849 94,949 95,959 96,269 96,469 96,769 97,379 97,579