The "proper" name is trihectaoctacontagon. Most people, including mathematicians, will use 380-gon since that effectively communicates the size of the polygon. But, if you want to appear pretentious or be obfuscatory, by all means use the Greek prefices.
name of 4000 sided polygon
The name of a 200 sided polygon is dihectagon.
The name of a 600 sided polygon is Hexcosiagon.
The name of a sided polygon is Octaconpentagon.
hexahectaheptacontakaidigon is the name of a 672 sided polygon
The name of a 12 sided polygon is Dodecagon.
A 8 sided polygon is called a octagon.
name of 4000 sided polygon
The name of a 18 sided polygon is Octadecagon.
The name of a 99 sided polygon is enneacontaenneagon.
The name of a 8 sided polygon is Octagon.
The name of a 19 sided polygon is enneadecagon.
The name of a 15 sided polygon is Pentadecagon.
The name of a 7 sided polygon is Heptagon.
The name of a 9 sided polygon is Nonagon.
The name of a 17 sided polygon is Heptadecagon.
The name of a 14 sided polygon is Tetradecagon.