Mystery Of The Permutable Primes

Number Theory Level 2

A prime number $p$ is a permutable prime if for all permutations of the digits of $p$ is also prime.

How many 2-digit permutable primes are there?

Details and Assumptions:

For example 113, 131 and 311 are all prime and this consists of all the permutations of 113, so they are all permutable primes.
Assume that we are only looking at numbers within a base 10 representation.