Sieved to P=160G

Primality testing 2^121555-7 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 19
Running N+1 test using discriminant 47, base 3+sqrt(47)
Calling N-1 BLS with factored part 0.17% and helper 0.01% (0.53% proof)
2^121555-7 is Fermat and Lucas PRP! (438.2806s+0.0025s)

To be completed...