10000...76353 (100-digits)

This number is a prime.

                                            1000000000 0000000000 0000000000
0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000076353

10^99 + 76353 is the smallest 100-digit prime that produces two other primes by changing only its first digit. I.e., 5*10^99 + 76353 and 7*10^99 + 76353 are primes. [Opao]