What are the divisors of 4087?

1, 61, 67, 4087

There is a total of 4 positive divisors.
The sum of these divisors is 4216.
The arithmetic mean is 1054.

4 odd divisors

1, 61, 67, 4087

How to compute the divisors of 4087?

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 4087 by each of the numbers from 1 to 4087 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)

4087 / 1 = 4087 (the remainder is 0, so 1 is a divisor of 4087)
4087 / 2 = 2043.5 (the remainder is 1, so 2 is not a divisor of 4087)
4087 / 3 = 1362.3333333333 (the remainder is 1, so 3 is not a divisor of 4087)
...
4087 / 4086 = 1.0002447381302 (the remainder is 1, so 4086 is not a divisor of 4087)
4087 / 4087 = 1 (the remainder is 0, so 4087 is a divisor of 4087)

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 4087 (i.e. 63.929648833698). 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 $\frac{N}{d} = D$ )

4087 / 1 = 4087 (the remainder is 0, so 1 and 4087 are divisors of 4087)
4087 / 2 = 2043.5 (the remainder is 1, so 2 is not a divisor of 4087)
4087 / 3 = 1362.3333333333 (the remainder is 1, so 3 is not a divisor of 4087)
...
4087 / 62 = 65.91935483871 (the remainder is 57, so 62 is not a divisor of 4087)
4087 / 63 = 64.873015873016 (the remainder is 55, so 63 is not a divisor of 4087)