Back Almost perfect number English Preskaŭ perfekta nombro Esperanto Número casi perfecto Spanish Lähes täydellinen luku Finnish Nombre presque parfait French מספר כמעט משוכלל HE Majdnem tökéletes számok Hungarian Bilangan hampir sempurna ID Numero lievemente difettivo Italian Bijna perfect getal Dutch
In math, an almost perfect number (also called slightly defective or least deficient number) is a type of natural number n. The sum of n's divisors must be equal to 2n − 1. Every known almost perfect number is a power of 2 and has non-negative exponents (sequence A000079 in the OEIS).