21 sided polygon: icosikaihenagon or henicosagon
The sum of the exterior angles of any polygon, regardless of the number of sides, is always 360 degrees. Therefore, the sum of the exterior angles of a 21-sided polygon is 360 degrees.
21
Icosikaihenagon, or also known as Henicosagon.
The sum of the angles of a polygon is equal to 180° times (n-2) where n is the number of sides.For a 23-sided polygon, that would give a total of (180°) x (21) = 3780°. If the angles are all the same, each would be 3780° ÷ 23 = 164.3478°
icosihenagon= 21-sided polygon icosihenagon= 21-sided polygon
The name of a 21 sided polygon is Icosihenagon.
21 sided polygon: icosikaihenagon or henicosagon
I suggest you forget about memorizing fancy names - which really serve no useful purpose - and just call them "20-sided polygon", "21-sided polygon", etc.
An icosikaihena is a polygon with 21 sides
The name of a 21 sided polygon is Icosihenagon.
The term for a 21 sided polygon is an icosikaihenagon. Icosi is the Greek for the numerical 20 and henagon means 1.
Icosagon
Though many polygons have a specific name not all do. It is accepted practice to use the number of sides as the name if one is not assigned (or known). A 21 sided polygon does not have a specific name so could quite reasonably be call a 21-ogon.
Icosikaihenagon
the icosikaihenagon is a 21 sided polygon
It's quite acceptable to call it a 21-agon but what's more important is knowing how to work out its properties