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Iran TST P2

Source: Iranian TST 2022 Problem 2

April 2, 2022
number theory

Problem Statement

For a positive integer nn, let τ(n)\tau(n) and σ(n)\sigma(n) be the number of positive divisors of nn and the sum of positive divisors of nn, respectively. let aa and bb be positive integers such that σ(an)\sigma(a^n) divides σ(bn)\sigma(b^n) for all nNn\in \mathbb{N}. Prove that each prime factor of τ(a)\tau(a) divides τ(b)\tau(b).
Proposed by MohammadAmin Sharifi