Definition:Almost Perfect Number

Definition
Let $n \in \Z_{\ge 0}$ be a positive integer.

Let $A \left({n}\right)$ denote the abundance of $n$.

$n$ is almost perfect $A \left({n}\right) = -1$.

Thus an almost perfect number can be described as "deficient, but only just".

Also see

 * Definition:Perfect Number
 * Definition:Quasiperfect
 * Definition:Abundance