 Deficient number

A positive integer whose proper-divisor sum is smaller than itself; equivalently, its sum-of-divisors function satisfies $\sigma (n)<2n$. For example, $s(8)=7<8$; also $s(1)=0<1$.

A deficient number is a positive integer \( n \) for which the sum of its proper divisors (excluding itself) is less than \( n \).