99999...00001 (84-digits)

This number is a prime.

                                                             9999 9999999999
0000000000 0000999999 9999999900 0000000000 0099999999 9999990000 0000000001

The largest prime factor of a googol plus 100. [Patterson]

Phi(196, 10) = Phi(7, -10^14) is the unique prime whose reciprocal has period 196 and is the largest known unique prime that is also an emirp (as of October 2010). [Chandler]