What are the divisors of 2149?

1, 7, 307, 2149

There is a total of 4 positive divisors.
The sum of these divisors is 2464.
The arithmetic mean is 616.

4 odd divisors

1, 7, 307, 2149

How to compute the divisors of 2149?

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 2149 by each of the numbers from 1 to 2149 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)

2149 / 1 = 2149 (the remainder is 0, so 1 is a divisor of 2149)
2149 / 2 = 1074.5 (the remainder is 1, so 2 is not a divisor of 2149)
2149 / 3 = 716.33333333333 (the remainder is 1, so 3 is not a divisor of 2149)
...
2149 / 2148 = 1.0004655493482 (the remainder is 1, so 2148 is not a divisor of 2149)
2149 / 2149 = 1 (the remainder is 0, so 2149 is a divisor of 2149)

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 2149 (i.e. 46.357307945997). 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 $\frac{N}{d} = D$ )

2149 / 1 = 2149 (the remainder is 0, so 1 and 2149 are divisors of 2149)
2149 / 2 = 1074.5 (the remainder is 1, so 2 is not a divisor of 2149)
2149 / 3 = 716.33333333333 (the remainder is 1, so 3 is not a divisor of 2149)
...
2149 / 45 = 47.755555555556 (the remainder is 34, so 45 is not a divisor of 2149)
2149 / 46 = 46.717391304348 (the remainder is 33, so 46 is not a divisor of 2149)