Nb. of divisors whose dec. representations ends with 1 or 9
Source: Germany Bundeswettbewerb Mathematik 2001, Round 1, Problem 4
February 1, 2009
number theoryprime factorizationprime numbersnumber theory unsolved
Problem Statement
Prove: For each positive integer is the number of divisors whose decimal representations ends with a 1 or 9 not less than the number of divisors whose decimal representations ends with 3 or 7.