I happen to notice the following interesting property of some of the prime integers: For example, 13 and it's permutation, 31 are primes. 17 and it's permutation 71 are both primes. But not 19 , it's permutation 91 is not a prime. Again, 3313 is prime, and one of it's permutation 3331 is also prime, however, none of the other permutations are prime such as 1333 or 3133.

I am wondering what are the frequency with which the following primes occur? Given a prime number, all the permutations of it's digits are also prime. Now I think it is almost non-existent beyond 2 digits numbers, but I want to know are there other prime numbers with such property?

On the other hand, I believe at least one permutation of the digits of a prime number is also prime will be much more frequent in nature. It would be interesting to find out when this occurs or do they have any special property?

Any thoughts ?

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