Infinitely many, assuming you are speaking in regards to either the radius or diameter, in which case can be taken at any angle from 360 to approaching 0.
A sphere.
A regular pentagon has zero perpendicular sides. If it is irregular, it could have as many as 2 or 4 perpendicular sides.
0 sides
An equilateral triangle doesn't have any perpendicular sides on it.
A rhombus has no perpendicular sides but its diagonals are perpendicular to each other and meet at right angles.
A sphere does not have any sides.
A right angle has one pair of perpendicular sides.
2, the two smallest sides are perpendicular to eachother.
A sphere has one side. Not tricky! Unless the sphere is hollow, which would have two sides, inside and outside.
Infinite.
none
Four