Found with PFGW Version 3.7.5

620^10857-10857^620 is 2-PRP! (15.5587s+0.0013s)
620^10857-10857^620 is 3-PRP! (16.0191s+0.0012s)
620^10857-10857^620 is 5-PRP! (15.9517s+0.0012s)
620^10857-10857^620 is 7-PRP! (15.9097s+0.0011s)
620^10857-10857^620 is 11-PRP! (16.1410s+0.0013s)

Primality testing 620^10857-10857^620 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 7
Running N+1 test using discriminant 13, base 1+sqrt(13)
Calling N+1 BLS with factored part 0.04% and helper 0.02% (0.13% proof)
620^10857-10857^620 is Fermat and Lucas PRP! (81.1475s+0.0020s)

To be completed...