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MathNet 2017-part-04 — 176 problems (EN–VI) Question 38

Math Olympiad Vault · MathNet 2017-part-04 — 176 problems (EN–VI)

Question 38

We are given the function $f: \mathbb{Z}_{\gt 0} \rightarrow \mathbb{Z}$ satisfying the properties:
(i) $f(p)=1$ for all prime numbers $p$,
(ii) $f(x y)=y f(x)+x f(y)$ for all $x, y \in \mathbb{Z}_{\gt 0}$.
Determine the smallest $n \geq 2016$ with $f(n)=n$.