#include <bits/stdc++.h>

using i64 = long long;
std::vector<int> minp, primes;

void sieve(int n) {
    minp.assign(n + 1, 0);
    primes.clear();
    
    for (int i = 2; i <= n; i++) {
        if (minp[i] == 0) {
            minp[i] = i;
            primes.push_back(i);
        }
        
        for (auto p : primes) {
            if (i * p > n) {
                break;
            }
            minp[i * p] = p;
            if (p == minp[i]) {
                break;
            }
        }
    }
}

void solve() {
    int n;
    std::cin >> n;
    
    sieve(n);
    
    std::vector<std::pair<int, int>> ans;
    std::vector<int> f(n + 1);
    for (int i = 3; i <= n; i += 2) {
        int p = minp[i];
        if (f[p] == 0) {
            f[p] = i;
        } else {
            ans.emplace_back(f[p], i);
            f[p] = 0;
        }
    }
    std::vector<int> even;
    for (int i = 1; i <= n / 2; i++) {
        if (f[i] != 0) {
            ans.emplace_back(f[i], 2 * i);
        } else {
            even.push_back(2 * i);
        }
    }
    for (int i = 1; i < even.size(); i += 2) {
        ans.emplace_back(even[i - 1], even[i]);
    }
    std::cout << ans.size();
    for (auto [x, y] : ans) {
        std::cout << " " << x << " " << y;
    }
    std::cout << "\n";
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t;
    std::cin >> t;
    
    while (t--) {
        solve();
    }
    
    return 0;
}