Let's say I want to check whether an integer is prime or not.

Implementation $$$1$$$:

bool is_prime1(long long n) {
    if (n < 2)
        return false;
    for (long long i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

Implementation $$$2$$$:

bool is_prime2(long long n) {
    if (n < 2)
        return false;
    for (long long i = 2; i <= n / i; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

Which implementation is better?