It's quite acceptable to call it a 99-agon but what's more important is knowing how to work out its properties.
Chat with our AI personalities
I would call it a 99-gon. However, if you wish to annoy your audience (unless they are Greek) or be pretentious, you could call it an enneacontanonagon.
ninetyanlamenteisfallernamnine is a 99 sided shape
The name of a 99 sided polygon is enneacontaenneagon.
The name for a 57 sided shape is derived by combining the name for a 50 sided shape with the name for a 7 sided shape. A 57 sided shape is called a pentacontaheptagon.
ennacontkaienneagon, or a ennacontenneagon
It is a 99-sided 2-dimensional shape (polygon).