What are the divisors of 2789?

1, 2789

There is a total of 2 positive divisors.
The sum of these divisors is 2790.
The arithmetic mean is 1395.

2 odd divisors

1, 2789

How to compute the divisors of 2789?

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 2789 by each of the numbers from 1 to 2789 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)

2789 / 1 = 2789 (the remainder is 0, so 1 is a divisor of 2789)
2789 / 2 = 1394.5 (the remainder is 1, so 2 is not a divisor of 2789)
2789 / 3 = 929.66666666667 (the remainder is 2, so 3 is not a divisor of 2789)
...
2789 / 2788 = 1.0003586800574 (the remainder is 1, so 2788 is not a divisor of 2789)
2789 / 2789 = 1 (the remainder is 0, so 2789 is a divisor of 2789)

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 2789 (i.e. 52.810983706044). 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 $\frac{N}{d} = D$ )

2789 / 1 = 2789 (the remainder is 0, so 1 and 2789 are divisors of 2789)
2789 / 2 = 1394.5 (the remainder is 1, so 2 is not a divisor of 2789)
2789 / 3 = 929.66666666667 (the remainder is 2, so 3 is not a divisor of 2789)
...
2789 / 51 = 54.686274509804 (the remainder is 35, so 51 is not a divisor of 2789)
2789 / 52 = 53.634615384615 (the remainder is 33, so 52 is not a divisor of 2789)