In geometry, an icosagon is a twenty-sided polygon. The sum of any icosagon's interior angles is 3240 degrees.
One interior angle in a regular icosagon is 162°, meaning that one exterior angle would be 18°.
The regular icosagon is a constructible polygon, by an edge-bisection of a regular decagon, and can be seen as a truncated decagon.
Read more about Icosagon: Uses