What are the divisors of 3815?

1, 5, 7, 35, 109, 545, 763, 3815

There is a total of 8 positive divisors.
The sum of these divisors is 5280.
The arithmetic mean is 660.

8 odd divisors

1, 5, 7, 35, 109, 545, 763, 3815

How to compute the divisors of 3815?

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 3815 by each of the numbers from 1 to 3815 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)

3815 / 1 = 3815 (the remainder is 0, so 1 is a divisor of 3815)
3815 / 2 = 1907.5 (the remainder is 1, so 2 is not a divisor of 3815)
3815 / 3 = 1271.6666666667 (the remainder is 2, so 3 is not a divisor of 3815)
...
3815 / 3814 = 1.0002621919245 (the remainder is 1, so 3814 is not a divisor of 3815)
3815 / 3815 = 1 (the remainder is 0, so 3815 is a divisor of 3815)

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 3815 (i.e. 61.765686266729). 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 $\frac{N}{d} = D$ )

3815 / 1 = 3815 (the remainder is 0, so 1 and 3815 are divisors of 3815)
3815 / 2 = 1907.5 (the remainder is 1, so 2 is not a divisor of 3815)
3815 / 3 = 1271.6666666667 (the remainder is 2, so 3 is not a divisor of 3815)
...
3815 / 60 = 63.583333333333 (the remainder is 35, so 60 is not a divisor of 3815)
3815 / 61 = 62.540983606557 (the remainder is 33, so 61 is not a divisor of 3815)