# Number is prime

JavaScript, Math, Algorithm · Jan 12, 2021

Checks if the provided integer is a prime number.

- Check numbers from
`2`

to the square root of the given number. - Return
`false`

if any of them divides the given number, else return`true`

, unless the number is less than`2`

.

```
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (let i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
```

`isPrime(11); // true`