## Is 219 a prime number?

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

For 219, the answer is: No, 219 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 219) is as follows: 1, 3, 73, 219.

To be 219 a prime number, it would have been required that 219 has only two divisors, i.e., itself and 1.

As a consequence:

To be 219 a prime number, it would have been required that 219 has only two divisors, i.e., itself and 1.

However, 219 is a **semiprime** (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 219 = 3 x 73, where 3 and 73 are both prime numbers.

## Is 219 a deficient number?

Yes, 219 is a deficient number, that is to say 219 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 219 without 219 itself (that is 1 + 3 + 73 = 77).

## Parity of 219

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

## Is 219 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 219 is about 14.799.

Thus, the square root of 219 is not an integer, and therefore 219 is not a square number.

## What is the square number of 219?

The square of a number (here 219) is the result of the product of this number (219) by itself (i.e., 219 × 219); the square of 219 is sometimes called "raising 219 to the power 2", or "219 squared".

The square of 219 is 47 961 because 219 × 219 = 219^{2} = 47 961.

As a consequence, 219 is the square root of 47 961.

## Number of digits of 219

219 is a number with 3 digits.

## What are the multiples of 219?

The multiples of 219 are all integers evenly divisible by 219, that is all numbers such that the remainder of the division by 219 is zero. There are infinitely many multiples of 219. The smallest multiples of 219 are:

- 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 219 too, since 0 × 219 = 0
- 219: indeed, 219 is a multiple of itself, since 219 is evenly divisible by 219 (we have 219 / 219 = 1, so the remainder of this division is indeed zero)
- 438: indeed, 438 = 219 × 2
- 657: indeed, 657 = 219 × 3
- 876: indeed, 876 = 219 × 4
- 1 095: indeed, 1 095 = 219 × 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 219). 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 14.799). 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.