The formal name is icosihexagon. Most people, including mathematicians, will use 26-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.
A five-sided polygon is called a pentagon.
A 39 sided polygon is called a 39-gon.
A thousand-sided polygon is a chiliagon.
hectoctagon is a 108 sided polygon
a hectoenneagon is a 109 sided polygon
A five sided polygon is called a pentagon because pentagon means five sided polygon I think.
A 26-gon
A million-sided polygon is called a megagon.
A 12-sided polygon is called a dodecagon.
A 20-sided polygon is called an icosagon.
A 14 sided polygon is called a tetradecagon.
A 90-sided polygon is called an enneacontagon.
A five-sided polygon is called a pentagon.
A 13 sided polygon is called a Tridecagon also a Triskaidecagon.
what is a 50 sided polygon called?
2000 sided polygon
A 8 sided polygon is called a octagon.