The product of two prime numbers is $1994$, what is their sum.
So if you look at the factors of $1994$, you have: $1,2,997,1994$. Since $1$ is not considered prime. then the two numbers are $2$ and $997$, so their sum is $999$.
But is there a way to the find the two products ($2$ and $997$) without trial and error?