99999...64781 (100-digits)

This number is a prime.

                                            9999999999 9999999999 9999999999
9999999999 9999999999 9999999999 9999999999 9999999999 9999999999 9999964781

This number is prime and the smallest of a pair of twin primes. The sum of the digits of this prime is 881 and the sum of the digits of the twin is 883. Note that 881 and 883 is a pair of twin primes. The two greatest twin primes of length 100 digits. [Cami]