A 16 sided polygon
If the interior angles add up to 1800 degrees then it is a 12 sided polygon.
The sum of the interior angles of a polygon with n sides is 180*(n-2) degrees.
The hexagon is the only one that has exactly 6. All polygons with 6 or more sides have at least 6 interior angles.
For any REGULAR n-sided polygon the interior angles are (180 - 360/n) degrees eg for a regular octagon, where n = 8, the calculation is 180 - 360/8 ie 180 - 45 = 135o degrees.