How it is calculated
If the sum of proper divisors is greater than the number, the number is abundant. If it is smaller, the number is deficient. The number 1 has no proper divisor in that sum, so its sum is zero.
Sum of proper divisors ? n
Where the numbers come from
- Number
Example
28 = 1 + 2 + 4 + 7 + 14. That is a perfect number.
Questions
Is 6 perfect too?
Yes: 1 + 2 + 3 = 6.
Which numbers are prime?
Deficient: the only proper divisor is 1.
A ceiling on the number?
Ten million, so running through the divisors stays fast.