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