I was doing a Mock AMC 10 (title) from AoPS (also title). I got really confused on number 21 because solution was bad.
Here it is:
A positive integer $n$ is called expoprime if for every prime $p$ dividing $n$, there exists a prime number $q$ such that $n$ is divisible by $p^q$ but not by $p^{q+1}$. Denote by the function $S(N)$ the sum of all divisors of $N$ that are expoprime. What is $S(2025) - S(2016)$?
Thanks in advance.