Perfect numbers
A kind of number
About Perfect numbers
A perfect number is a positive integer that equals the sum of its proper positive divisors (excluding itself). For example, 6 = 1 + 2 + 3. It is unknown whether there are infinitely many or any odd perfect numbers.
Key features
- All known perfect numbers are even and have the form 2ᵖ⁻¹(2ᵖ − 1) where 2ᵖ − 1 is a Mersenne prime.
- Only 51 perfect numbers are currently known.
Examples: