Found with PFGW Version 3.7.5

28^27375-27375^28 is 2-PRP! (33.3549s+0.0012s)
28^27375-27375^28 is 3-PRP! (34.1971s+0.0013s)
28^27375-27375^28 is 5-PRP! (34.2291s+0.0012s)
28^27375-27375^28 is 7-PRP! (34.4533s+0.0015s)
28^27375-27375^28 is 11-PRP! (35.1851s+0.0012s)

Primality testing 28^27375-27375^28 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 3
Running N+1 test using discriminant 11, base 2+sqrt(11)
Calling N-1 BLS with factored part 0.01% and helper 0.00% (0.03% proof)
28^27375-27375^28 is Fermat and Lucas PRP! (167.6020s+0.0021s)

To be completed...