Need Assistance with Large Number division

[RepsForJesus]

Hello all,
For a project in school, I need to encrypt some text using the RSA algorithm, and I need to generate two large primes (bigger than any type) doing so. The process of which I am going to go about doing a check if the numbers generated are prime, is to first check if that number doesn't divide with the numbers 1 - 10,000. Then after that apply it to a Miller-Rabin test. But here's where I am stuck. I am working on code on dividing one of the large numbers with the smaller numbers and I'm not sure if I'm doing this correctly.

Please, can you look over my code and tell me where you think I'm doing something incorrectly?
Thanks!

#include <iostream>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;

typedef vector<int> ivec;
ivec number;

//this is just to output the vector, to see the number in the console
ostream &operator << (ostream &stream, ivec &obj)
{
    for (unsigned int i = 0; i < (int)obj.size(); i++)
    {
        stream << obj[i] << " ";
    }
    return stream;
}

int divide(vector<int> number, int divisor, vector<int> origNum)
{
    vector<int> remain;
    int sumRemainder = 0;
    
    for (int i = 0; i < number.size(); i++)
    {
        long long sumDigit = number[i];
        if (divisor > sumDigit)
        {
            for (int j = 0; ; j++)
            {
                if (number[i] == 0)
                    sumDigit += pow(10, j);
                else
                    sumDigit += (pow(10, j) * (number[j]));
                
                if (sumDigit > divisor)
                    break;
                
                if (j > i)
                {
                    cout << "Sorry can't divide this number." <<endl;
                    break;
                }
                
            }
            
        }
        int counter;
        for (int k = 0; ; k++)
        {
            divisor *= k;
            if (divisor > sumDigit)
                break;
            counter++;
        }
        
        sumDigit -= divisor;
        remain.push_back(sumDigit);
        if (sumDigit == 0 || divisor > sumDigit)
            remain.push_back(number[i+1]);
        
        divide(remain, divisor, number);
    }
    
    for (int l = 0; ; l++)
    {
        if (number[l] == 0)
            sumRemainder += pow(10, l);
        else
            sumRemainder += pow(10, l) * (number[l]);
    }
    
    return sumRemainder;
}


int main(int argc, const char * argv[])
{
    srand(time(NULL));
    for(int i = 1; i <= 617; i++)
    {
        number.push_back(rand() % 10);
    }
    cout << number <<endl;
    int remainder = divide(number, 123, number); 
    //I just chose a random number to divide
    return 0;
}