70115921domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes that are congruent to -1 mod n, where n is the index of the prime.at n=21A052013Primes p such that pi(p) divides p-1 and/or p+1, where pi(p) is the number of primes <= p.at n=33A162567Primes p such that sigma(p)/pi(p) is prime.at n=8A269022Prime numbersat n=4124466