How many vertices does an icosahedron have?

There is no simple answer to this question.

Polyhedra are named according to the number of faces that they have. An icosahedron is a 3-dimensional shape with 20 faces. It could be in the form of a pyramid with a 19-sided polygon as base. In that case, it has 20 vertices. Or it could be in the form of a prism with 18-sided polygons as base and in that case it has 36 vertices. There are several million different configurations, and the number of vertices varies.

The regular icosahedron is a Platonic solid with faces that are equilateral triangles. That has 12 vertices.