What are the divisors of 4129?

1, 4129

There is a total of 2 positive divisors.
The sum of these divisors is 4130.
The arithmetic mean is 2065.

2 odd divisors

1, 4129

How to compute the divisors of 4129?

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 4129 by each of the numbers from 1 to 4129 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)

4129 / 1 = 4129 (the remainder is 0, so 1 is a divisor of 4129)
4129 / 2 = 2064.5 (the remainder is 1, so 2 is not a divisor of 4129)
4129 / 3 = 1376.3333333333 (the remainder is 1, so 3 is not a divisor of 4129)
...
4129 / 4128 = 1.000242248062 (the remainder is 1, so 4128 is not a divisor of 4129)
4129 / 4129 = 1 (the remainder is 0, so 4129 is a divisor of 4129)

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 4129 (i.e. 64.257295305669). 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 $\frac{N}{d} = D$ )

4129 / 1 = 4129 (the remainder is 0, so 1 and 4129 are divisors of 4129)
4129 / 2 = 2064.5 (the remainder is 1, so 2 is not a divisor of 4129)
4129 / 3 = 1376.3333333333 (the remainder is 1, so 3 is not a divisor of 4129)
...
4129 / 63 = 65.539682539683 (the remainder is 34, so 63 is not a divisor of 4129)
4129 / 64 = 64.515625 (the remainder is 33, so 64 is not a divisor of 4129)