MathDB
Dangerous numbers

Source: Russian TST 2021, Day 6 P3

March 21, 2023
number theorynumber base

Problem Statement

Given an integer m>1m > 1, we call the number xx{} dangerous if xx{} divides the number yy{}, which is obtained by writing the digits of xx{} in base mm{} in reverse order, with xyx\neq y. Prove that if there exists a three-digit (in base mm) dangerous number for a given mm, then there exists a two-digit (in base mm) dangerous number.