Is 865 a prime number?

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

For 865, the answer is: No, 865 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 865) is as follows: 1, 5, 173, 865.

For 865 to be a prime number, it would have been required that 865 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

Actually, one can immediately see that 865 cannot be prime, because 5 is one of its divisors: indeed, a number ending with 0 or 5 has necessarily 5 among its divisors. The last digit of 865 is 5, so it is divisible by 5 and is therefore not prime.

As a consequence:

865 is a multiple of 1
865 is a multiple of 5
865 is a multiple of 173

For 865 to be a prime number, it would have been required that 865 has only two divisors, i.e., itself and 1.

However, 865 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 865 = 5 x 173, where 5 and 173 are both prime numbers.

Is 865 a deficient number?

Yes, 865 is a deficient number, that is to say 865 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 865 without 865 itself (that is 1 + 5 + 173 = 179).

Parity of 865

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

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What is an even number?

Is 865 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 865 is about 29.411.

Thus, the square root of 865 is not an integer, and therefore 865 is not a square number.

What is the square number of 865?

The square of a number (here 865) is the result of the product of this number (865) by itself (i.e., 865 × 865); the square of 865 is sometimes called "raising 865 to the power 2", or "865 squared".

The square of 865 is 748 225 because 865 × 865 = 865² = 748 225.

As a consequence, 865 is the square root of 748 225.

Number of digits of 865

865 is a number with 3 digits.

What are the multiples of 865?

The multiples of 865 are all integers evenly divisible by 865, that is all numbers such that the remainder of the division by 865 is zero. There are infinitely many multiples of 865. The smallest multiples of 865 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 865 too, since 0 × 865 = 0
865: indeed, 865 is a multiple of itself, since 865 is evenly divisible by 865 (we have 865 / 865 = 1, so the remainder of this division is indeed zero)
1 730: indeed, 1 730 = 865 × 2
2 595: indeed, 2 595 = 865 × 3
3 460: indeed, 3 460 = 865 × 4
4 325: indeed, 4 325 = 865 × 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 865). 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 29.411). 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 865

Preceding numbers: …863, 864
Following numbers: 866, 867…

Nearest numbers from 865

Preceding prime number: 863
Following prime number: 877