612041

This number is a prime.

The smallest Honaker prime p such that replacing each digit d in decimal expansion of p with d^3 yields a new prime when done recursively three times, i.e., 612041 -> 216180641 (prime); 216180641 -> 8121615120216641 (prime); 8121615120216641 -> 512181216112518081216216641 (prime). [Bajpai]