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",
11 (number) 11 (number) 11 (eleven) is the natural number following 10 and preceding 12. It is the first repdigit. In English, it is the smallest positive integer requiring three syllables and the largest prime number with a single-morpheme name. Eleven derives from the Old English ' which is first attested in Bede's late 9th-century "Ecclesiastical History of the English People". It has cognates in every Germanic language (for example, German "elf"), whose Proto-Germanic ancestor has been reconstructed as *"ainalifa-", from the prefix *"aina-" (adjectival "one") and suffix *"-lifa-" of uncertain meaning. It is sometimes compared with the Lithuanian ', although ""