Primality testing 31728^39089-39089^31728 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 5
Running N-1 test using base 7
Running N-1 test using base 13
Running N+1 test using discriminant 19, base 1+sqrt(19)
Calling N-1 BLS with factored part 0.00% and helper 0.00% (0.02% proof)
31728^39089-39089^31728 is Fermat and Lucas PRP! (1799.2860s+0.0051s)

Sieved with xyyxsieve

To be completed...