MathDB
d(n) is the largest divisor of the odd number n, different from n

Source: Balkan BMO Shortlist 2016 N2

July 30, 2019
divisormaximumnumber theoryoddIMO Shortlist

Problem Statement

Find all odd natural numbers nn such that d(n)d(n) is the largest divisor of the number nn different from nn. (d(n)d(n) is the number of divisors of the number n including 11 and nn ).
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