C#: sumOfFactorsPrime

private int sumOfFactorsPrime(int number, int[] primelist) {
    int n = number;
    int sum = 1;
    int p = primelist[0];
    int j;
    int i = 0;
 
    while (p * p <= n && n > 1 && i < primelist.Length) {
        p = primelist[i];
        i++;
        if (n % p == 0) {
            j = p * p;
            n = n / p;
            while (n % p == 0) {
                j = j * p;
                n = n / p;
            }
            sum = sum * (j - 1) / (p - 1);
        }
    }
 
    //A prime factor larger than the square root remains
    if (n > 1) {
        sum *= n + 1;
    }
    return sum - number;
}