No, because the base of the triangle can be basically any polygon, and only a triangle with an equilateral triangle is a platonic solid.
To be more specific, only a regular tetrahedron, in which all 4 triangular faces are equilateral, is a platonic solid. Any triangular pyramid is a tetrahedron, but not necessarily a regular tetrahedron. The pyramids in Egypt and Central America are square pyramids, by the way, not triangular.
There (not their) are 5 platonic solids.
We don't know for certain who discovered the platonic solids first. However, Pythagoras is credited by some sources as discovering the platonic solids first. Other sources credit Theaetetus as being the first to describe all five platonic solids and proving that these are the *only* platonic solids.
The book called Platonic Solids: The experience
There are different numbers on the different platonic solids.
They're all three-dimensional.