56 (number)
56 (fifty-six) is the natural number following 55 and preceding 57. Mathematics 56 is: The sum of the first six triangular numbers (making it a tetrahedral number). The number of ways to choose 3 out of 8 objects or 5 out of 8 objects, if order does not matter. The sum of six consecutive primes (3 + 5 + 7 + 11 + 13 + 17) a tetranacci number and as a multiple of 7 and 8, a pronic number. Interestingly it is one of a few pronic numbers whose digits in decimal also are successive (5 and 6). a refactorable number, since 8 is one of its 8 divisors. The sum of the sums of the divisors of the first 8 positive integers. A semiperfect number, since 56 is twice a perfect number. A partition number – the number of distinct ways 11 can be represented as the sum of natural numbers. An Erdős–Woods number, since it is possible to find sequences of 56 consecutive integers such that each inner member shares a factor with either the first or the last member. The only known number n such that , where φ(m) is Euler's totient function and σ(n) is