Found with PFGW Version 3.4.6

21^11680+20 is 2-PRP! (8.1125s+0.0068s)
21^11680+20 is 3-PRP! (8.0705s+0.0046s)
21^11680+20 is 5-PRP! (8.0757s+0.0078s)
21^11680+20 is 7-PRP! (8.5755s+0.0046s)
21^11680+20 is 11-PRP! (8.4623s+0.0042s)

Primality testing 21^11680+20 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Running N+1 test using discriminant 7, base 2+sqrt(7)
Calling N+1 BLS with factored part 0.17% and helper 0.05% (0.57% proof)
21^11680+20 is Fermat and Lucas PRP! (81.9236s+0.0110s)

To be completed...