Found with PFGW Version 3.7.5

1642^6405-6405^1642 is 2-PRP! (16.2498s+0.0019s)
1642^6405-6405^1642 is 3-PRP! (16.4910s+0.0025s)
1642^6405-6405^1642 is 5-PRP! (17.4107s+0.0019s)
1642^6405-6405^1642 is 7-PRP! (20.6582s+0.0026s)
1642^6405-6405^1642 is 11-PRP! (18.7589s+0.0026s)

Primality testing 1642^6405-6405^1642 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 3
Running N-1 test using base 5
Running N+1 test using discriminant 11, base 3+sqrt(11)
Calling N-1 BLS with factored part 0.09% and helper 0.03% (0.30% proof)
1642^6405-6405^1642 is Fermat and Lucas PRP! (98.9031s+0.0040s)

To be completed...