IBM Research

PUZZLE   IBM-306

Non-palindromic numbers with palindromic squares

IBM Research · Ponder This · 2023-10

IBM Ponder This #306 · October 2023

This riddle was suggested by our previous puzzlemaster, Oded Margalit. Thanks Oded!

We are entering the 26th year of Ponder This and this is the 307th riddle. Both 26 and 307 are not palindromes, but their squares 676 and 94249 are.

Your goal: Find a number n that is not a palindrome, such that n2 is a palindrome and n845(mod 1201)

A Bonus "*" will be given for finding that number, such that in addition to the previous constraints, we also have n2256(mod 3565)

An open question that we are pondering about: Does there exist an n that is not a palindrome but n2 is, such that all the digits of n (in base 10) are odd?

Solution

Best opened after a real attempt

To be added.