165. Find all pairs of integers, the sum of which is equal to their product.
165. Denoting the required numbers by $x$ and $y$, we have:

$$
x+y=x y
$$

or

$$
\begin{aligned}
& x y-x-y+1=1 \\
& (x-1)(y-1)=1
\end{aligned}
$$

Since 1 can only be factored into integer factors in two ways, we immediately obtain:

$$
x-1=1, y-1=1 ; x=2, y=2
$$

or

$$
x-1=-1, y-1=-1 ; x=0, y=0
$$