It is acomposite number, with its proper divisors being 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110, making it anamicable number with284.[1][2] Every number up to 220 may be expressed as a sum of its divisors, making 220 apractical number.[3]
It is the sum of four consecutive primes (47 + 53 + 59 + 61).[4] It is the smallest even number with the property that when represented as a sum of two prime numbers (perGoldbach's conjecture) both of the primes must be greater than or equal to 23.[5]There are exactly 220 different ways ofpartitioning 64 = 82 into a sum ofsquare numbers.[6]
It is atetrahedral number, the sum of the first tentriangular numbers,[7] and a dodecahedral number.[8] If all of the diagonals of a regulardecagon are drawn, the resulting figure will have exactly 220 regions.[9]
