Found with PFGW Version 3.6.0

21^21960+20 is 2-PRP! (10.5633s+0.0026s)
21^21960+20 is 3-PRP! (10.5387s+0.0038s)
21^21960+20 is 5-PRP! (10.5338s+0.0026s)
21^21960+20 is 7-PRP! (10.5017s+0.0038s)
21^21960+20 is 11-PRP! (10.4973s+0.0037s)

Primality testing 21^21960+20 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Running N-1 test using base 3
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 0.03% and helper 0.02% (0.10% proof)
21^21960+20 is Fermat and Lucas PRP! (94.7966s+0.0023s)

To be completed...