What are the divisors of 3139?

1, 43, 73, 3139

There is a total of 4 positive divisors.
The sum of these divisors is 3256.
The arithmetic mean is 814.

4 odd divisors

1, 43, 73, 3139

How to compute the divisors of 3139?

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 3139 by each of the numbers from 1 to 3139 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)

3139 / 1 = 3139 (the remainder is 0, so 1 is a divisor of 3139)
3139 / 2 = 1569.5 (the remainder is 1, so 2 is not a divisor of 3139)
3139 / 3 = 1046.3333333333 (the remainder is 1, so 3 is not a divisor of 3139)
...
3139 / 3138 = 1.0003186743149 (the remainder is 1, so 3138 is not a divisor of 3139)
3139 / 3139 = 1 (the remainder is 0, so 3139 is a divisor of 3139)

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 3139 (i.e. 56.026779311326). 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 $\frac{N}{d} = D$ )

3139 / 1 = 3139 (the remainder is 0, so 1 and 3139 are divisors of 3139)
3139 / 2 = 1569.5 (the remainder is 1, so 2 is not a divisor of 3139)
3139 / 3 = 1046.3333333333 (the remainder is 1, so 3 is not a divisor of 3139)
...
3139 / 55 = 57.072727272727 (the remainder is 4, so 55 is not a divisor of 3139)
3139 / 56 = 56.053571428571 (the remainder is 3, so 56 is not a divisor of 3139)