Is 646 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

For 646, the answer is: No, 646 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 646) is as follows: 1, 2, 17, 19, 34, 38, 323, 646.

For 646 to be a prime number, it would have been required that 646 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

As a consequence:

646 is a multiple of 1
646 is a multiple of 2
646 is a multiple of 17
646 is a multiple of 19
646 is a multiple of 34
646 is a multiple of 38
646 is a multiple of 323

For 646 to be a prime number, it would have been required that 646 has only two divisors, i.e., itself and 1.

Is 646 a deficient number?

Yes, 646 is a deficient number, that is to say 646 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 646 without 646 itself (that is 1 + 2 + 17 + 19 + 34 + 38 + 323 = 434).

Parity of 646

646 is an even number, because it is evenly divisible by 2: 646 / 2 = 323.

Find out more:

What is an even number?

Is 646 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 646 is about 25.417.

Thus, the square root of 646 is not an integer, and therefore 646 is not a square number.

What is the square number of 646?

The square of a number (here 646) is the result of the product of this number (646) by itself (i.e., 646 × 646); the square of 646 is sometimes called "raising 646 to the power 2", or "646 squared".

The square of 646 is 417 316 because 646 × 646 = 646² = 417 316.

As a consequence, 646 is the square root of 417 316.

Number of digits of 646

646 is a number with 3 digits.

What are the multiples of 646?

The multiples of 646 are all integers evenly divisible by 646, that is all numbers such that the remainder of the division by 646 is zero. There are infinitely many multiples of 646. The smallest multiples of 646 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 646 too, since 0 × 646 = 0
646: indeed, 646 is a multiple of itself, since 646 is evenly divisible by 646 (we have 646 / 646 = 1, so the remainder of this division is indeed zero)
1 292: indeed, 1 292 = 646 × 2
1 938: indeed, 1 938 = 646 × 3
2 584: indeed, 2 584 = 646 × 4
3 230: indeed, 3 230 = 646 × 5
etc.

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 646). 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 25.417). 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 646

Preceding numbers: …644, 645
Following numbers: 647, 648…

Nearest numbers from 646

Preceding prime number: 643
Following prime number: 647