Lychrel number Created 2026-10-20 Updated 2026-11-05
A Lychrel number is a positive integer whose repeated reverse-and-add process never reaches a palindromic number in the chosen radix. Each step performs digit reversal and adds the reversed integer to the current value. For example, reaches a decimal palindrome in one step, so is not a base-ten Lychrel number.
Failure to reach a palindromic number within a fixed iteration limit establishes only a candidate. It does not prove that every later step also fails. A computation must therefore distinguish a bounded search result from the infinite claim in the definition.