Problem

Source: Own. IMO 2021 Malaysian Training Camp 1

Tags: number theory, Divisors, Perfect Numbers



Given a natural number $n$, call a divisor $d$ of $n$ to be $\textit{nontrivial}$ if $d>1$. A natural number $n$ is $\textit{good}$ if one or more distinct nontrivial divisors of $n$ sum up to $n-1$. Prove that every natural number $n$ has a multiple that is good.