# 180 (number)

 ← 179 180 181 →
Cardinalone hundred eighty
Ordinal180th
(one hundred eightieth)
Factorization22 × 32 × 5
Divisors1, 2, 3, 4, 5, 6, 9, 10, 12, 15, 18, 20, 30, 36, 45, 60, 90, 180
Greek numeralΡΠ´
Roman numeralCLXXX
Binary101101002
Ternary202003
Octal2648
Duodecimal13012

180 (one hundred [and] eighty) is the natural number following 179 and preceding 181.

## In mathematics

180 is an abundant number, with its proper divisors summing up to 366. 180 is also a highly composite number, a positive integer with more divisors than any smaller positive integer. One of the consequences of 180 having so many divisors is that it is a practical number, meaning that any positive number smaller than 180 that is not a divisor of 180 can be expressed as the sum of some of 180's divisors. 180 is a refactorable number.

180 is the sum of two square numbers: 122 + 62. 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 180.

180 is a Harshad number in base 10, and in binary it is a digitally balanced number, since its binary representation has the same number of zeros as ones (10110100).

## In religion

The Book of Genesis says that Isaac died at the age of 180.