About the Perfect Number Checker
Check if a number is perfect, abundant or deficient by comparing it with the sum of its proper divisors.
Also known as: is perfect number, abundant number, deficient number, aliquot sum.
How to use this calculator
- Enter whole number.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Perfect: σ(n) − n = n
Worked example
Using the values pre-filled in the calculator above:
- Whole number = 28
the calculator returns:
- Classification: Perfect number
- Sum of proper divisors: 28