Polygon

The EXterior angles will be    180 - 162 = 18 degrees

     EXterior angles sum to 360

        360 / 18 = n

You could also write it as an equation:

$n$ = number of sides in the polygon

$162n=180(n-2)$

$162n=180n-360$

$0=18n-360$

$18n=360$

$n = 20$

So, the polygon has $\color{brown}\boxed{20}$ sides like Pavlov said.

(His method is the better method tho...)