180 (number) two square numbers: 12 + 6. It can be expressed as either the sum of six consecutive prime numbers: 19 + 23 + 29 + 31 + 37 + 41, or the sum of eight consecutive prime numbers: 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37. 180 is an Ulam number, which can be expressed as a sum of earlier terms in the Ulam sequence only as 177 + 3. 180 is a 61-gonal number. Half a circle has 180 degrees. Summing Euler's totient function φ("x") over the first + 24 integers gives
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 ""