Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In mathematics, a hexadecagon (sometimes called a hexakaidecagon) is a polygon with 16 sides and 16 vertices. A regular hexadecagon is constructible with a compass and straightedge. Each angle of a regular hexadecagon is 157.5 degrees, and the total angle measure of any hexadecagon is 2520 degrees. Only the regular ones have been studied in any depth; star polygons in general appear not to have been formally defined. They should not be confused with star domains.