What are the divisors of 4017?

1, 3, 13, 39, 103, 309, 1339, 4017

There is a total of 8 positive divisors.
The sum of these divisors is 5824.
The arithmetic mean is 728.

8 odd divisors

1, 3, 13, 39, 103, 309, 1339, 4017

How to compute the divisors of 4017?

A number N is said to be divisible by a number M (with M non-zero) if, when we divide N by M, the remainder of the division is zero.

$N mod M = 0$

Brute force algorithm

We could start by using a brute-force method which would involve dividing 4017 by each of the numbers from 1 to 4017 to determine which ones have a remainder equal to 0.

$Remainder = N - (M \times ⌊ \frac{N}{M} ⌋)$

(where $⌊ \frac{N}{M} ⌋$ is the integer part of the quotient)

4017 / 1 = 4017 (the remainder is 0, so 1 is a divisor of 4017)
4017 / 2 = 2008.5 (the remainder is 1, so 2 is not a divisor of 4017)
4017 / 3 = 1339 (the remainder is 0, so 3 is a divisor of 4017)
...
4017 / 4016 = 1.0002490039841 (the remainder is 1, so 4016 is not a divisor of 4017)
4017 / 4017 = 1 (the remainder is 0, so 4017 is a divisor of 4017)

Improved algorithm using square-root

However, there is another slightly better approach that reduces the number of iterations by testing only integers less than or equal to the square root of 4017 (i.e. 63.379807509963). Indeed, if a number N has a divisor D greater than its square root, then there is necessarily a smaller divisor d such that:

$D \times d = N$

(thus, if $\frac{N}{D} = d$ , then $\frac{N}{d} = D$ )

4017 / 1 = 4017 (the remainder is 0, so 1 and 4017 are divisors of 4017)
4017 / 2 = 2008.5 (the remainder is 1, so 2 is not a divisor of 4017)
4017 / 3 = 1339 (the remainder is 0, so 3 and 1339 are divisors of 4017)
...
4017 / 62 = 64.790322580645 (the remainder is 49, so 62 is not a divisor of 4017)
4017 / 63 = 63.761904761905 (the remainder is 48, so 63 is not a divisor of 4017)