Tridecagon

A tridecagon or trikaidecagon or triskaidecagon or trisdecagon or 13-gon is a shape with 13 sides and 13 corners.
Regular tridecagon.
All sides of a regular tridecagon are the same length. Each corner is 147.27°. All corners added together equal 6840°.
Area.
The amount of space a regular tridecagon takes up is
"a" is the length of one of its sides.
Numismatic use.
The regular tridecagon is used as the shape of the Czech 20 korun coin.