Is 641 a prime number?

641 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 641 is about 25.318.

Thus, the square root of 641 is not an integer, and therefore 641 is not a square number.

Anyway, 641 is a prime number, and a prime number cannot be a perfect square.

The square of a number (here 641) is the result of the product of this number (641) by itself (i.e., 641 × 641); the square of 641 is sometimes called "raising 641 to the power 2", or "641 squared".

The square of 641 is 410 881 because 641 × 641 = 641² = 410 881.

As a consequence, 641 is the square root of 410 881.

641 is a number with 3 digits.

The multiples of 641 are all integers evenly divisible by 641, that is all numbers such that the remainder of the division by 641 is zero. There are infinitely many multiples of 641. The smallest multiples of 641 are:

• 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 641 too, since 0 × 641 = 0
• 641: indeed, 641 is a multiple of itself, since 641 is evenly divisible by 641 (we have 641 / 641 = 1, so the remainder of this division is indeed zero)
• 1 282: indeed, 1 282 = 641 × 2
• 1 923: indeed, 1 923 = 641 × 3
• 2 564: indeed, 2 564 = 641 × 4
• 3 205: indeed, 3 205 = 641 × 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 641). 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 25.318). 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: …639, 640
• Following numbers: 642, 643…

Nearest numbers from 641

• Preceding prime number: 631
• Following prime number: 643

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• 641 est-il un nombre premier ?