What are the divisors of 3955?

1, 5, 7, 35, 113, 565, 791, 3955

There is a total of 8 positive divisors.
The sum of these divisors is 5472.
The arithmetic mean is 684.

8 odd divisors

1, 5, 7, 35, 113, 565, 791, 3955

How to compute the divisors of 3955?

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 3955 by each of the numbers from 1 to 3955 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)

3955 / 1 = 3955 (the remainder is 0, so 1 is a divisor of 3955)
3955 / 2 = 1977.5 (the remainder is 1, so 2 is not a divisor of 3955)
3955 / 3 = 1318.3333333333 (the remainder is 1, so 3 is not a divisor of 3955)
...
3955 / 3954 = 1.0002529084471 (the remainder is 1, so 3954 is not a divisor of 3955)
3955 / 3955 = 1 (the remainder is 0, so 3955 is a divisor of 3955)

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 3955 (i.e. 62.88879073412). 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 $\frac{N}{d} = D$ )

3955 / 1 = 3955 (the remainder is 0, so 1 and 3955 are divisors of 3955)
3955 / 2 = 1977.5 (the remainder is 1, so 2 is not a divisor of 3955)
3955 / 3 = 1318.3333333333 (the remainder is 1, so 3 is not a divisor of 3955)
...
3955 / 61 = 64.83606557377 (the remainder is 51, so 61 is not a divisor of 3955)
3955 / 62 = 63.790322580645 (the remainder is 49, so 62 is not a divisor of 3955)