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2022 MMATHS Individual p10 - sum of f(d) when d|M

Source:

October 1, 2023
number theoryprime numbersMMATHS

Problem Statement

Define a function ff on the positive integers as follows: f(n)=mf(n) = m, where mm is the least positive integer such that nn is a factor of m2m^2. Find the smallest integer MM such that M\sqrt{M} is both a product of prime numbers, of which there are at least 33, and a factor of dMf(d),\sum_{ d|M} f(d), the sum of f(d)f(d) for all positive integers dd that divide MM.