[algs_easy] Determine if a number is prime

Definition of a prime number: a number greater than 1 that has no true factors

int isPrime(int n) {
    if(n <= 1) return 0;
    for(int m = 2; m * m <= n; m++)
        if(n % m == 0) return 0;    // not a prime
    return 1;
}

Please think about why  it can be ignored when m * m > n  ?