Integral divisor of a whole number that is different from itself.

### Property

The set of proper divisors of a prime number is the singleton {1}.

### Notation

The set of proper divisors of a number *n* is noted as div_{p}(*n*).

### Example

The set of proper divisors of 60 is: div_{p}(60) = {1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30}.