CAT (QA) PYQs

The number of positive integers less than $50$, having exactly two distinct factors other than $1$ and itself, is

If $m$ and $n$ are natural numbers such that $n > 1$, and $m^{n}=2^{25} \times 3^{40}$, then $m-n$ equals

How many pairs $(a, b)$ of positive integers are there such that $a \le b$ and $ab =$ $4^{2017}$?