Is 651 a prime number?

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

For 651, the answer is: No, 651 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 651) is as follows: 1, 3, 7, 21, 31, 93, 217, 651.

For 651 to be a prime number, it would have been required that 651 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

As a consequence:

651 is a multiple of 1
651 is a multiple of 3
651 is a multiple of 7
651 is a multiple of 21
651 is a multiple of 31
651 is a multiple of 93
651 is a multiple of 217

For 651 to be a prime number, it would have been required that 651 has only two divisors, i.e., itself and 1.

Is 651 a deficient number?

Yes, 651 is a deficient number, that is to say 651 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 651 without 651 itself (that is 1 + 3 + 7 + 21 + 31 + 93 + 217 = 373).

Parity of 651

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

Find out more:

What is an even number?

Is 651 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 651 is about 25.515.

Thus, the square root of 651 is not an integer, and therefore 651 is not a square number.

What is the square number of 651?

The square of a number (here 651) is the result of the product of this number (651) by itself (i.e., 651 × 651); the square of 651 is sometimes called "raising 651 to the power 2", or "651 squared".

The square of 651 is 423 801 because 651 × 651 = 651² = 423 801.

As a consequence, 651 is the square root of 423 801.

Number of digits of 651

651 is a number with 3 digits.

What are the multiples of 651?

The multiples of 651 are all integers evenly divisible by 651, that is all numbers such that the remainder of the division by 651 is zero. There are infinitely many multiples of 651. The smallest multiples of 651 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 651 too, since 0 × 651 = 0
651: indeed, 651 is a multiple of itself, since 651 is evenly divisible by 651 (we have 651 / 651 = 1, so the remainder of this division is indeed zero)
1 302: indeed, 1 302 = 651 × 2
1 953: indeed, 1 953 = 651 × 3
2 604: indeed, 2 604 = 651 × 4
3 255: indeed, 3 255 = 651 × 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 651). 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 25.515). 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 651

Preceding numbers: …649, 650
Following numbers: 652, 653…

Nearest numbers from 651

Preceding prime number: 647
Following prime number: 653