Is 815 a prime number? What are the divisors of 815?

## Parity of 815

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

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## Is 815 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 815 is about 28.548.

Thus, the square root of 815 is not an integer, and therefore 815 is not a square number.

## What is the square number of 815?

The square of a number (here 815) is the result of the product of this number (815) by itself (i.e., 815 × 815); the square of 815 is sometimes called "raising 815 to the power 2", or "815 squared".

The square of 815 is 664 225 because 815 × 815 = 8152 = 664 225.

As a consequence, 815 is the square root of 664 225.

## Number of digits of 815

815 is a number with 3 digits.

## What are the multiples of 815?

The multiples of 815 are all integers evenly divisible by 815, that is all numbers such that the remainder of the division by 815 is zero. There are infinitely many multiples of 815. The smallest multiples of 815 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 815). 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 28.548). 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 815

• Preceding numbers: …813, 814
• Following numbers: 816, 817

### Nearest numbers from 815

• Preceding prime number: 811
• Following prime number: 821
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