olymmath

HMMT 2016 U31

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For a positive integer nn, denote by τ(n)\tau(n) the number of positive integer divisors of nn, and denote by ϕ(n)\phi(n) the number of positive integers that are less than or equal to nn and relatively prime to nn. Call a positive integer nn good if φ(n)+4τ(n)=n\varphi(n)+4 \tau(n)=n. For example, the number 44 is good because φ(44)+4τ(44)=44\varphi(44)+4 \tau(44)=44. Find the sum of all good positive integers nn.

Dataset text NuminaMath olympiads. Quoted with source.

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