What is it called a 26 sided polyhedgon?

Answer 1

If you wish to communicate information, I suggest you call it an 26-gon. Although there is a prefix for 26 I suggest you keep it simple. Not only is the use of long Greek prefices pretentious, you will only annoy the reader who will probably have to consult a dictionary. Having said that, if you do want to be pretentious or obfuscate, you can use the link below for polygons with up to 999 sides. http://faculty.kutztown.edu/schaeffe/Tutorials/General/Polygons.html