What are the divisors of 3813?

1, 3, 31, 41, 93, 123, 1271, 3813

There is a total of 8 positive divisors.
The sum of these divisors is 5376.
The arithmetic mean is 672.

8 odd divisors

1, 3, 31, 41, 93, 123, 1271, 3813

How to compute the divisors of 3813?

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 3813 by each of the numbers from 1 to 3813 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)

3813 / 1 = 3813 (the remainder is 0, so 1 is a divisor of 3813)
3813 / 2 = 1906.5 (the remainder is 1, so 2 is not a divisor of 3813)
3813 / 3 = 1271 (the remainder is 0, so 3 is a divisor of 3813)
...
3813 / 3812 = 1.0002623294858 (the remainder is 1, so 3812 is not a divisor of 3813)
3813 / 3813 = 1 (the remainder is 0, so 3813 is a divisor of 3813)

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 3813 (i.e. 61.749493925052). 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 $\frac{N}{d} = D$ )

3813 / 1 = 3813 (the remainder is 0, so 1 and 3813 are divisors of 3813)
3813 / 2 = 1906.5 (the remainder is 1, so 2 is not a divisor of 3813)
3813 / 3 = 1271 (the remainder is 0, so 3 and 1271 are divisors of 3813)
...
3813 / 60 = 63.55 (the remainder is 33, so 60 is not a divisor of 3813)
3813 / 61 = 62.508196721311 (the remainder is 31, so 61 is not a divisor of 3813)