How many two digit numbers have exactly 4 positive factors? (Here 1...

Two digit numbers with 4 positive factors are either the product of two prime numbers or perfect cubes. i.e. $2 \cdot 5,2 \cdot 7$, $\_\_\_\_$ 2.47 3.5, 3.7, 3.11, $\_\_\_\_$ 3.31 5.7, 5.11, 5.13, $\_\_\_\_$ 5.19 7.11, 7.13; and $3^3$ Total numbers $=30$