Is 129 a prime number? What are the divisors of 129?

## Is 129 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

For 129, the answer is: No, 129 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 129) is as follows: 1, 3, 43, 129.

To be 129 a prime number, it would have been required that 129 has only two divisors, i.e., itself and 1.

As a consequence:

• 129 is a multiple of 1
• 129 is a multiple of 3
• 129 is a multiple of 43

To be 129 a prime number, it would have been required that 129 has only two divisors, i.e., itself and 1.

However, 129 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 129 = 3 x 43, where 3 and 43 are both prime numbers.

## Is 129 a deficient number?

Yes, 129 is a deficient number, that is to say 129 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 129 without 129 itself (that is 1 + 3 + 43 = 47).

## Parity of 129

129 is an odd number, because it is not evenly divisible by 2.

## Is 129 a perfect square number?

A number is a perfect square (or a square number) if its square root is an integer; that is to say, it is the product of an integer with itself. Here, the square root of 129 is about 11.358.

Thus, the square root of 129 is not an integer, and therefore 129 is not a square number.

## What is the square number of 129?

The square of a number (here 129) is the result of the product of this number (129) by itself (i.e., 129 × 129); the square of 129 is sometimes called "raising 129 to the power 2", or "129 squared".

The square of 129 is 16 641 because 129 × 129 = 1292 = 16 641.

As a consequence, 129 is the square root of 16 641.

## Number of digits of 129

129 is a number with 3 digits.

## What are the multiples of 129?

The multiples of 129 are all integers evenly divisible by 129, that is all numbers such that the remainder of the division by 129 is zero. There are infinitely many multiples of 129. The smallest multiples of 129 are:

• 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 129 too, since 0 × 129 = 0
• 129: indeed, 129 is a multiple of itself, since 129 is evenly divisible by 129 (we have 129 / 129 = 1, so the remainder of this division is indeed zero)
• 258: indeed, 258 = 129 × 2
• 387: indeed, 387 = 129 × 3
• 516: indeed, 516 = 129 × 4
• 645: indeed, 645 = 129 × 5
• etc.

## How to determine whether an integer is a prime number?

To determine the primality of a number, several algorithms can be used. The most naive technique is to test all divisors strictly smaller to the number of which we want to determine the primality (here 129). First, we can eliminate all even numbers greater than 2 (and hence 4, 6, 8…). Then, we can stop this check when we reach the square root of the number of which we want to determine the primality (here the square root is about 11.358). Historically, the sieve of Eratosthenes (dating from the Greek mathematics) implements this technique in a relatively efficient manner.

More modern techniques include the sieve of Atkin, probabilistic algorithms, and the cyclotomic AKS test.

## Numbers near 129

• Preceding numbers: …127, 128
• Following numbers: 130, 131

## Nearest numbers from 129

• Preceding prime number: 127
• Following prime number: 131
Find out whether some integer is a prime number