Found with PFGW Version 3.7.5

1869^6640-6640^1869 is 2-PRP! (19.2921s+0.0024s)
1869^6640-6640^1869 is 3-PRP! (18.8007s+0.0020s)
1869^6640-6640^1869 is 5-PRP! (18.6711s+0.0032s)
1869^6640-6640^1869 is 7-PRP! (19.5329s+0.0028s)
1869^6640-6640^1869 is 11-PRP! (19.8084s+0.0021s)

Primality testing 1869^6640-6640^1869 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 3
Running N-1 test using base 7
Running N+1 test using discriminant 17, base 6+sqrt(17)
Calling N-1 BLS with factored part 0.05% and helper 0.01% (0.17% proof)
1869^6640-6640^1869 is Fermat and Lucas PRP! (116.1507s+0.0035s)

To be completed...