And here is its evil twin: i.e. all digits are "7"s, except for one and two "9"s.

(7*10^10014+18*10^3046+11)/9 (PRP) and

(7*10^10014+18*10^3046-7)/9 (PRP)

ECPP proofs are in progress.

There is also a 6655-digit pair using only "3"s and "1"s (proven primes)

(10^6655-6*10^4147-7)/3

(10^6655-6*10^4147-1)/3

M.Kamada collects

these records.