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
17 (number) 17 (number) 17 (seventeen) is the natural number following 16 and preceding 18. It is a prime number. In English speech, the numbers 17 and 70 are sometimes confused, as they sound very similar. The number 17 has wide significance in pure mathematics, as well as in applied sciences, law, music, religion, sports, and other cultural phenomena. Seventeen is the sum of the first four prime numbers. Seventeen is the seventh prime number. The next prime is nineteen, with which it forms a twin prime. Seventeen is a permutable prime and a supersingular prime. Seventeen is the third Fermat prime,