Found with PFGW Version 3.7.5

166^20853-20853^166 is 2-PRP! (40.7028s+0.0015s)
166^20853-20853^166 is 3-PRP! (40.6887s+0.0016s)
166^20853-20853^166 is 5-PRP! (40.6852s+0.0015s)
166^20853-20853^166 is 7-PRP! (40.5674s+0.0015s)
166^20853-20853^166 is 11-PRP! (40.6682s+0.0014s)

Primality testing 166^20853-20853^166 [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 0.02% and helper 0.02% (0.09% proof)
166^20853-20853^166 is Fermat and Lucas PRP! (202.8399s+0.0028s)

To be completed...