Deficient number checker

Check if a number is deficient. A number is deficient if the sum of its proper divisors is less than itself.

Number

Deficient numbers

A number is deficient if σ(n) − n < n. Most numbers are deficient. All prime numbers are deficient (proper divisors sum to 1). All powers of 2 are deficient.

Example

8: proper divisors = 1+2+4 = 7 < 8 → deficient. The "deficiency" is 8 − 7 = 1.