The 13 interior angles of a 13 sided polygon add up to 1,980 degrees
The sum of the interior angles of a n-sided polygon is (n-2)*180 degrees. So for 13 sides, the sum is 11*180 = 1980 degrees.
The sum of the exterior angles is always 360 degrees.
A 13 sided polygon is called a Tridecagon also a Triskaidecagon.
The name of a 21 sided polygon is Icosihenagon.
The name of a 16 sided polygon is Hexadecagon.
Sum of exterior angles of any sided polygon is 360 so sum of exterior angle of 6 sided polygon (hexagon) is 360
The interior sum of a 12 sided polygon is 1800.
The sum of the interior angles of a four-sided polygon is 360 degrees.