A permutable prime, also called an absolute prime, is a prime number that remains prime after every permutation of its decimal digits. Repeated digits give repeated permutations and do not change the condition. For example, 113 is permutable because 113, 131, and 311 are all prime, whereas 137 is not because 371 is composite.
Every multidigit permutable prime uses only the digits 1, 3, 7, and 9. Permutable primality depends on the chosen number base and is stronger than circular primality.
