Is 281 a prime number?

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

Find out more:

• What is an even 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 281 is about 16.763.

Thus, the square root of 281 is not an integer, and therefore 281 is not a square number.

Anyway, 281 is a prime number, and a prime number cannot be a perfect square.

The square of a number (here 281) is the result of the product of this number (281) by itself (i.e., 281 × 281); the square of 281 is sometimes called "raising 281 to the power 2", or "281 squared".

The square of 281 is 78 961 because 281 × 281 = 281² = 78 961.

As a consequence, 281 is the square root of 78 961.

281 is a number with 3 digits.

The multiples of 281 are all integers evenly divisible by 281, that is all numbers such that the remainder of the division by 281 is zero. There are infinitely many multiples of 281. The smallest multiples of 281 are:

• 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 281 too, since 0 × 281 = 0
• 281: indeed, 281 is a multiple of itself, since 281 is evenly divisible by 281 (we have 281 / 281 = 1, so the remainder of this division is indeed zero)
• 562: indeed, 562 = 281 × 2
• 843: indeed, 843 = 281 × 3
• 1 124: indeed, 1 124 = 281 × 4
• 1 405: indeed, 1 405 = 281 × 5
• etc.

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 281). 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 16.763). 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.

• Preceding numbers: …279, 280
• Following numbers: 282, 283…

Nearest numbers from 281

• Preceding prime number: 277
• Following prime number: 283

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• 281 est-il un nombre premier ?