75555555557domain: NAppears in sequencesPrimes which are a sandwich of numbers made of only one digit between two 7's.at n=12A068688Smallest palindromic prime containing exactly n 5's.at n=8A083976Palindromic primes in which all internal digits are 5.at n=6A108842Largest n-digit prime with the most digits equal to 5.at n=10A178003