What do you call a 45 sided shape?

Answer 1

A 45-sided shape is called a pentatetracontagon. But, actually, if you want to keep it simple, you can just append the suffix -gon to the end of a number (higher than 10 only), like 12-gon, or 56-gon, or 89-gon or 1,000,000,000-gon, et cetera.