Tricontagon
A 38-sided polygon is called a triacontakaioctagon. The naming convention for polygons follows the Greek numerical prefixes for the number of sides, in this case "tri" for 3 and "contakai" for 10, along with the suffix "-gon" for polygon. Therefore, a 38-sided polygon is a triacontakaioctagon.
It contains 36 triangles
They add up to 6480 degrees
A five sided polygon is called a pentagon because pentagon means five sided polygon I think.
An 11 sided polygon is a hendecagon and a 12 sided polygon is a dodecagon