72727

This number is a prime.

The sum of the digits of the first 72 primes is 727, another palindromic prime. Submitted on 7/27. [Trotter]

prime(prime(prime(prime(prime(one dozen))))). [Merickel]

The largest prime-digit palindromic prime time occurring at prime hours, prime minutes, and prime seconds, on a 12-hour digital clock. [Loungrides]