What is a 49 sided shape called?

A 49-sided polygon is called a tetracontakaienneagon. The name is derived from the Greek prefixes tetraconta- (meaning forty) and ennea- (meaning nine) and the suffix -agon (meaning angle). The internal angles of a regular tetracontakaienneagon measure 171.43 degrees, and it has 49 sides and 49 vertices.