244247domain: NPropertiesPrimalityPrimeyesAppears in sequencesPrimes that remain prime through 3 iterations of function f(x) = 8x + 1.at n=25A023291Primes that are concatenations of n with n + 3.at n=28A032626Primes having only {2, 4, 7} as digits.at n=36A385784Prime numbersat n=21565