Efficiently getting all divisors of a given number

Here's my code:

#include <bits/stdc++.h>

using namespace std;

#define pii pair<int, int>

#define MAX 46656

#define LMT 216

#define LEN 4830

#define RNG 100032

unsigned base[MAX / 64], segment[RNG / 64], primes[LEN];

#define sq(x) ((x)*(x))

#define mset(x,v) memset(x,v,sizeof(x))

#define chkC(x,n) (x[n>>6]&(1<<((n>>1)&31)))

#define setC(x,n) (x[n>>6]|=(1<<((n>>1)&31)))

// http://zobayer.blogspot.com/2009/09/segmented-sieve.html

void sieve()

{

    unsigned i, j, k;

    for (i = 3; i<LMT; i += 2)

        if (!chkC(base, i))

            for (j = i*i, k = i << 1; j<MAX; j += k)

                setC(base, j);

    primes[0] = 2;

    for (i = 3, j = 1; i<MAX; i += 2)

        if (!chkC(base, i))

            primes[j++] = i;

}

//http://www.geeksforgeeks.org/print-all-prime-factors-of-a-given-number/

vector <pii> factors;

void primeFactors(int num)

{

    int expo = 0;   

    for (int i = 0; primes[i] <= sqrt(num); i++)

    {

        expo = 0;

        int prime = primes[i];

        while (num % prime == 0){

            expo++;

            num = num / prime;

        }

        if (expo>0)

            factors.push_back(make_pair(prime, expo));

    }

    if ( num >= 2)

        factors.push_back(make_pair(num, 1));

}

vector <int> divisors;

void setDivisors(int n, int i) {

    int j, x, k;

    for (j = i; j<factors.size(); j++) {

        x = factors[j].first * n;

        for (k = 0; k<factors[j].second; k++) {

            divisors.push_back(x);

            setDivisors(x, j + 1);

            x *= factors[j].first;

        }

    }

}

int main() {

    sieve();

    int n, x, i; 

    cin >> n;

    for (int i = 0; i < n; i++) {

        cin >> x;

        primeFactors(x);

        setDivisors(1, 0);

        divisors.push_back(1);

        sort(divisors.begin(), divisors.end());

        cout << divisors.size() << "\n";

        for (int j = 0; j < divisors.size(); j++) {

            cout << divisors[j] << " "; 

        }

        cout << "\n";

        divisors.clear();

        factors.clear();

    }

}

The first part, sieve() is used to find the prime numbers and put them in primes[] array. Follow the link to find more about that code (bitwise sieve).

The second part primeFactors(x) takes an integer (x) as input and finds out its prime factors and corresponding exponent, and puts them in vector factors[]. For example, primeFactors(12) will populate factors[] in this way:

    factors[0].first=2, factors[0].second=2
    factors[1].first=3, factors[1].second=1

as 12 = 2^2 * 3^1

The third part setDivisors() recursively calls itself to calculate all the divisors of x, using the vector factors[] and puts them in vector divisors[].

It can calculate divisors of any number which fits in int. Also it is quite fast.