Is 649 a prime number? What are the divisors of 649?

## Parity of 649

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

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## Is 649 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 649 is about 25.475.

Thus, the square root of 649 is not an integer, and therefore 649 is not a square number.

## What is the square number of 649?

The square of a number (here 649) is the result of the product of this number (649) by itself (i.e., 649 × 649); the square of 649 is sometimes called "raising 649 to the power 2", or "649 squared".

The square of 649 is 421 201 because 649 × 649 = 6492 = 421 201.

As a consequence, 649 is the square root of 421 201.

## Number of digits of 649

649 is a number with 3 digits.

## What are the multiples of 649?

The multiples of 649 are all integers evenly divisible by 649, that is all numbers such that the remainder of the division by 649 is zero. There are infinitely many multiples of 649. The smallest multiples of 649 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 649). 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 25.475). 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 649

• Preceding numbers: …647, 648
• Following numbers: 650, 651

### Nearest numbers from 649

• Preceding prime number: 647
• Following prime number: 653
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