This article is from the Puzzles FAQ, by Chris Cole email@example.com and Matthew Daly firstname.lastname@example.org with numerous contributions by others.
Does the series formed by adding a number to its reversal always end in
This is not known.
If you start with 196, after 9480000 iterations you get a 3924257-digit
non-palindromic number. However, there is no known proof that you will
never get a palindrome.
The statement is provably false for binary numbers. Roland Sprague has
shown that 10110 starts a series that never goes palindromic.