135211

This number is a prime.

The smallest prime p such that replacing each digit d in decimal expansion of p with d^2 yields alternately a new semiprime and a new sphenic number when done recursively six times, e.g., 135211 -> 1925411 (semiprime), 1925411 -> 1814251611 (sphenic number), 1814251611 -> 16411642513611 (semiprime), 16411642513611 -> 13616113616425193611 (sphenic number), 13616113616425193611 -> 1936136119361361642518193611 (semiprime), 1936136119361361642518193611 -> 1819361936118193619361361642516418193611 (sphenic number). [Bajpai]