Rank2
TypeRegular
SpaceSpherical
Notation
Coxeter diagramx19o
Schläfli symbol{19}
Elements
Edges19
Vertices19
Measures (edge length 1)
Circumradius${\displaystyle \frac{1}{2\sin\frac{\pi}{19}} ≈ 3.03777}$
Inradius${\displaystyle \frac{1}{2\tan\frac{\pi}{19}} ≈ 2.99634}$
Area${\displaystyle \frac{19}{4\tan\frac{\pi}{19}} ≈ 28.46519}$
Angle${\displaystyle \frac{17\pi}{19} ≈ 161.05263°}$
Central density1
Number of pieces19
Level of complexity1
Related polytopes
Army{19}
Conjugate8 total
Abstract properties
Euler characteristic0
Topological properties
OrientableYes
Properties
SymmetryI2(19), order 38
ConvexYes
NatureTame

The enneadecagon is a polygon with 19 sides. A regular enneadecagon has equal sides and equal angles.

A circle with radius 3 centered at the center of an enneadecagon intersects its sides. This is related to the fact that 19/3 ≈ 2π.