deficient number

noun Mathematics.

a positive number that is greater than the sum of all positive integers that are submultiples of it, as 10, which is greater than the sum of 1, 2, and 5.

Compare abundant number, perfect number.

Origin of deficient number

First recorded in 1720–30

Also called defective number.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018