180

180 is an abundant number, with its proper divisors summing up to 366. 180 is also the 11th highly composite number, a positive integer with 18 divisors, more 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 Harshad number and a refactorable number.