almost perfect number

An almost perfect number or least deficient number is a number n whose proper divisors add up to just one less than itself. That is, σ(n)-n=n-1, with σ(n) being the sum of divisors function. Currently, the only known almost perfect numbers are the integer powers of 2 (e.g., 1, 2, 4, 8, 16, 32, 64, 128, etc.) No one has been able to prove that there are almost perfect numbers of a different form.

Title almost perfect number
Canonical name AlmostPerfectNumber
Date of creation 2013-03-22 17:41:51
Last modified on 2013-03-22 17:41:51
Owner PrimeFan (13766)
Last modified by PrimeFan (13766)
Numerical id 4
Author PrimeFan (13766)
Entry type Definition
Classification msc 11A05
Synonym least deficient number
Related topic QuasiperfectNumber