16065...77221 (25-digits)

This number is a prime.

                                                 16065 7703611442 7599277221

The trio of primes 89, 6017226864647074440629, and 1606577036114427599277221 is the largest known trio of primes {A, B, C} such that the prime factorization of A^2 + B^2 + C^2 is 3 * A * B * C. [Tolgede]