A diacosipentacontaheptagon is a polygon with 257 sides, it's internal angle is 178.6 degrees.

It is not visually distinguishable from a circle, and it's perimeter differs from the circumference of the circle by 24 parts per million.

The dihectapentacontaheptagon is constructible, as 257 is a Fermat number, along with 3, 5, 17 and 65537.

Community content is available under CC-BY-SA unless otherwise noted.