icosihenagonal
An icosihenagon is a polygon with 21 sides and 21 vertices. The word "icosihenagon" is derived from the Greek words "eíkosi" meaning twenty and "hēnná" meaning one, and "gōnia" meaning corner or angle.
In a regular icosihenagon, all sides are of equal length, and all interior angles are equal. The
The measure of each interior angle in a regular icosihenagon is 3420 degrees / 21, which is approximately
The number of diagonals in an icosihenagon can be calculated using the formula n(n-3)/2. For an icosihenagon,