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MathNet 2017-part-01 — 176 problems (EN–VI) Question 101

Math Olympiad Vault · MathNet 2017-part-01 — 176 problems (EN–VI)

Question 101

To determine the number of positive divisors of a number, it suffices to factor it into powers of distinct primes and multiply the successors of the exponents. For example, $2016=2^{5} \cdot 3^{2} \cdot 5^{1}$ has $(5+1)(2+1)(1+1)=36$ positive divisors. Consider the number $n=2^{7} \cdot 3^{4}$.

a) Determine the number of positive divisors of $n^{2}$.

b) How many divisors of $n^{2}$ are greater than $n$?

c) How many divisors of $n^{2}$ are greater than $n$ and are not multiples of $n$?