This is a rare 711..11 near-repunit unprovable PRP: only a few tiny primes are known and an 83462-digit PRP (see http://mada.la.coocan.jp/nrr/7/71111.htm )
PFGW test will take a very long time. I recommend either Prime95 PRP (optionally with a few threads), or LLR with the following input
64 10 762811 -1 9
On a modern CPU (with AVX), this test will take less than an hour for a Strong Fermat PRP test and then another couple of hours for Strong Fermat, Lucas and Frobenius tests.
To be completed...