71428571domain: NPropertiesPrimalityPrimeyesAppears in sequencesa(n) = floor(10^9/n).at n=13A033423Primes formed by the initial digits of the decimal expansion of 1/14, starting at the first nonzero digit in the expansion.at n=2A242827Prime numbers of the form floor((j/7)*10^k) where 1 <= j <= 6 and k >= 1.at n=9A343833Prime numbersat n=4197106