69709723domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumbers k such that prime(k) == 9 (mod k).at n=20A023151Least positive integer m with pi(m*n) = phi(m), where pi(.) is the prime-counting function and phi(.) is Euler's totient function.at n=19A247601Prime numbersat n=4102057