It's quite acceptable to call it a 21-agon but what's more important is knowing how to work out its properties
The name of a 21 sided polygon is Icosihenagon.
The name of a 21 sided polygon is Icosihenagon.
icosihenagon= 21-sided polygon icosihenagon= 21-sided polygon
The names of polygons with sides ranging from 21 to 30 are as follows: a 21-sided polygon is called a icosagon, a 22-sided polygon is a dicosagon, a 23-sided polygon is a tricosagon, a 24-sided polygon is a tetracosagon, a 25-sided polygon is a pentacosagon, a 26-sided polygon is a hexacosagon, a 27-sided polygon is a heptacosagon, a 28-sided polygon is an octacosagon, a 29-sided polygon is a nonacosagon, and a 30-sided polygon is a triacontagon.
An icosikaihena is a polygon with 21 sides
a triple heptagon.
The name of a 12 sided polygon is Dodecagon.
A 8 sided polygon is called a octagon.
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.
name of 4000 sided polygon
The term for a 21 sided polygon is an icosikaihenagon. Icosi is the Greek for the numerical 20 and henagon means 1.
The name of a 10 sided polygon is Decagon.