Is Prime?

const isPrime = (num: number): boolean => {
    if (num <= 1) return false;
    if (num > 2 && num % 2 === 0) return false;

    const sqrt = ~~Math.sqrt(num);

    for (let i = 3; i <= sqrt; i += 2)
        if (num % i === 0)
            return false;

    return true;
}