It is called a megagon. A ∞ sided shape is called an apeirogon.
megagon (hecatomyriagon)
Megagon
megagon
megagon
I have no idea But it would look a lot like a sphere
A million-sided polygon is called a "megagon", from "mega-" meaning "great" or "million". A regular megagon has a million angles, each equal to 179.99964°. As such, a regular megagon is practically indistinguishable from a circle.
Megagon
1 million.
megagon
megagon
A megagon.