Prime quadruplet 23620, 152141, 1028789, 7188960, 51672312, 381226246, 2873279651 . The constant representing the sum of the reciprocals of all prime quadruplets, Brun's constant for prime quadruplets, denoted by "B", is the sum of the reciprocals of all prime quadruplets: with value: This constant should not be confused with the Brun's constant for cousin primes, prime pairs of the form ("p", "p" + 4), which is also written as "B". The prime quadruplet {11, 13, 17, 19} is alleged to appear on the Ishango bone although this is disputed. Excluding the first prime quadruplet, the shortest possible distance between two quadruplets {"p",
400 (number) = 2 × 101, Mertens function returns 0, nontotient, noncototient. 405 = 3 × 5, Mertens function returns 0, Harshad number; 406 = 2 × 7 × 29, sphenic number, triangular number, centered nonagonal number, nontotient 407 = 11 × 37, 408 = 2 × 3 × 17 409 is a prime number, Chen prime, centered triangular number. 410 = 2 × 5 × 41, sphenic number, sum of six consecutive primes (59 + 61 + 67 + 71 + 73 + 79), nontotient, Harshad number 411 = 3 × 137, self number, 412 = 2 × 103, nontotient, noncototient,