;Definitions
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 also be prime. 

For example:
'''1193''' is a circular prime, since '''1931''', '''9311''' and '''3119''' are all also prime.

Note that a number which is a cyclic permutation of a smaller circular prime is not considered to be itself a circular prime. So '''13''' is a circular prime, but '''31''' is not. 


A '''repunit''' (denoted by R) is a number whose base 10 representation contains only the digit '''1'''.

For example:
R(2) = 11 and R(5) = 11111 are repunits.


;Task
* Find the first 19 circular primes.


* If your language has access to arbitrary precision integer arithmetic, given that they are all repunits, find the next 4 circular primes.


* (Stretch) Determine which of the following repunits are probably circular primes: R(5003), R(9887), R(15073), R(25031), R(35317) and R(49081). The larger ones may take a long time to process so just do as many as you reasonably can.


;See also
* [[wp:Circular_prime|Wikipedia article - Circular primes]].
* [[wp:Repunit|Wikipedia article - Repunit]].
* [[oeis:A016114|OEIS sequence A016114 - Circular primes]].