Is 261 a prime number? What are the divisors of 261?

## Parity of 261

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

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## Is 261 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 261 is about 16.155.

Thus, the square root of 261 is not an integer, and therefore 261 is not a square number.

## What is the square number of 261?

The square of a number (here 261) is the result of the product of this number (261) by itself (i.e., 261 × 261); the square of 261 is sometimes called "raising 261 to the power 2", or "261 squared".

The square of 261 is 68 121 because 261 × 261 = 2612 = 68 121.

As a consequence, 261 is the square root of 68 121.

## Number of digits of 261

261 is a number with 3 digits.

## What are the multiples of 261?

The multiples of 261 are all integers evenly divisible by 261, that is all numbers such that the remainder of the division by 261 is zero. There are infinitely many multiples of 261. The smallest multiples of 261 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 261). 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 16.155). 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 261

• Preceding numbers: …259, 260
• Following numbers: 262, 263

### Nearest numbers from 261

• Preceding prime number: 257
• Following prime number: 263
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