Is 820 a prime number? What are the divisors of 820?

## Parity of 820

820 is an even number, because it is evenly divisible by 2: 820 / 2 = 410.

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## Is 820 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 820 is about 28.636.

Thus, the square root of 820 is not an integer, and therefore 820 is not a square number.

## What is the square number of 820?

The square of a number (here 820) is the result of the product of this number (820) by itself (i.e., 820 × 820); the square of 820 is sometimes called "raising 820 to the power 2", or "820 squared".

The square of 820 is 672 400 because 820 × 820 = 8202 = 672 400.

As a consequence, 820 is the square root of 672 400.

## Number of digits of 820

820 is a number with 3 digits.

## What are the multiples of 820?

The multiples of 820 are all integers evenly divisible by 820, that is all numbers such that the remainder of the division by 820 is zero. There are infinitely many multiples of 820. The smallest multiples of 820 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 820). 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 28.636). 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 820

• Preceding numbers: …818, 819
• Following numbers: 821, 822

### Nearest numbers from 820

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