palindromeQ[n_Integer] := Block[{digits = IntegerDigits[n]}, digits == Reverse@digits] nextNumber[n_Integer] := n + FromDigits[Reverse@IntegerDigits@n] lychrelQ[n_Integer] := ! palindromeQ@ Catch[Nest[If[palindromeQ[#], Throw[#], nextNumber[#]] &, nextNumber[n], 500]]