My sorting program seems to glitch out whenever I give it a number that increments to quickly

Question

I'm trying to make program to sort numbers higher to lower from left to right, and it seems to glitch whenever the number increments too soon. I tried a handful of inputs:

42145 Sorted to 54421, correct;

41245 Sorted to 54221, wrong but almost right;

1021 Sorted to 2210, wrong but almost right;

254321234 Sorted to 555555552, very much wrong.

Is it just my method of sorting or did I do something wrong? Code:

#include <iostream>
#include <vector>
#include <math.h>
#include <string>
#include <sstream>
using namespace std;
 
uint64_t descend(uint64_t num) {
    vector<uint64_t> numVect;
    int numLength = 1;
    uint64_t numTmp = num;
    stringstream output;
    uint64_t result;
 
    //Find the length of the entered number
    while (true) {
        numTmp /= 10;
        if (numTmp > 0)
            numLength++;
        else
            break;
    }
 
    //Make the entered number into a vector
    for (int i = 1; i < numLength + 1; i++) {
        numTmp = num / pow(10, numLength - i);
        numTmp %= 10;
        numVect.push_back(numTmp);
    }
 
    //Sort the numbers in the vector
    for (int j = 0; j < numLength; j++) {
        numTmp = numVect[j];
        for (int i = j; i < numLength; i++) {
            if (numTmp < numVect[i]) {
                numVect.insert(numVect.begin()+j, numVect[i]);
                numVect.erase(numVect.end() - 1);
                break;
            }
        }
    }
 
    //Convert the vector to a regular number and return
    for (int i = 0; i < numLength; i++) {
        output << numVect[i];
    }
    output >> result;
    return result;
}
 
int main() {
    uint64_t output;
    cin >> output;
    output = descend(output);
    cout << "output: " << output << endl;
    return 0;
}

Answer 1

int descend(int num) {
    vector<int> numVect;
    int result = 0;

    while (num) {
        numVect.push_back(num % 10);
        num /= 10;
    }

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

    for (int i = 0; i < numVect.size(); i++) {
        result += numVect[i] * pow(10, numVect.size() - i - 1);
        cout << result;
    }
    return result;
}

int main()
{
    int output;
    cin >> output;
    output = descend(output);
    cout << "output: " << output << endl;
    return 0;
}