Rubik's Cube has 54 Facets

Theorem
Let $S$ be the set of facets of Rubik's cube.

Then the cardinality of $S$ is given by:
 * $\card S = 54$

That is:
 * A Rubik's cube has $54$ facets.

Proof
A cube, by definition, has $6$ faces.

Each face is subdivided into $9$ facets.

Hence there are $6 \times 9 = 54$ facets in total.