$P$ and $Q$ are two integers such that $P \times Q = 64$. Which of the following cannot be the value of $P+Q$?

Factor of $64$ are: $1,2,4,8,16,32,64$.

It is given that $P\times Q=64$. The number of pairs of $(P\times Q)=64$ are:

So from above Option (D) is not possible.