It's Thursday, so it's time for another code puzzler. The idea is simple: solve the coding problem as efficiently as you can, in any language or framework that you find suitable.
Note: Even though there really is nothing stopping you from finding a solution to this on the internet, try to keep honest, and come up with your own answer. It's all about the participation!
A circular prime is a prime number with the property that the number generated at each intermediate step when cyclically permuting its (base 10) digits will be prime. For example 1193 is a circular prime, since 1931, 9311 and 3119 all are also prime.
Your task is to calculate how many circular primes exist below 1 million.
Catch up on all our previous puzzlers here