Is 686 a prime number? What are the divisors of 686?

## Parity of 686

686 is an even number, because it is evenly divisible by 2: 686 / 2 = 343.

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## Is 686 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 686 is about 26.192.

Thus, the square root of 686 is not an integer, and therefore 686 is not a square number.

## What is the square number of 686?

The square of a number (here 686) is the result of the product of this number (686) by itself (i.e., 686 × 686); the square of 686 is sometimes called "raising 686 to the power 2", or "686 squared".

The square of 686 is 470 596 because 686 × 686 = 6862 = 470 596.

As a consequence, 686 is the square root of 470 596.

## Number of digits of 686

686 is a number with 3 digits.

## What are the multiples of 686?

The multiples of 686 are all integers evenly divisible by 686, that is all numbers such that the remainder of the division by 686 is zero. There are infinitely many multiples of 686. The smallest multiples of 686 are:

## 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 686). 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 26.192). 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 686

• Preceding numbers: …684, 685
• Following numbers: 687, 688

### Nearest numbers from 686

• Preceding prime number: 683
• Following prime number: 691
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