#include <bits/stdc++.h>
using namespace std;
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char& s) {
  string res = "'";
  res += s;
  res += "'";
  return res;
}
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (i) res += ", ";
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
long long check(long long x) {
  if (x == 1) return 1;
  for (long long i = 2; i * i <= x; i++)
    if (x % i == 0) {
      return 1;
    }
  return 0;
}
void solve() {
  long long k;
  string s;
  cin >> k >> s;
  map<char, long long> a;
  for (auto c : s) {
    a[c]++;
    if (c != '2' && c != '3' && c != '5' && c != '7') {
      cout << 1 << '\n' << c << '\n';
      return;
    }
  }
  for (auto [c, cnt] : a) {
    if (cnt >= 2) {
      cout << 2 << '\n' << c << c << '\n';
      return;
    }
  }
  string ans = "11111";
  function<void(long long, long long, string)> solve =
      [&](long long i, long long x, string res) {
        if ((long long)(res).size() && check(x) &&
            (long long)(res).size() < (long long)(ans).size()) {
          ans = res;
        }
        if (i == k) return;
        solve(i + 1, x, res);
        solve(i + 1, x * 10 + (s[i] - '0'), res + s.substr(i, 1));
      };
  solve(0, 0, "");
  cout << (long long)(ans).size() << '\n' << ans << '\n';
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long q;
  cin >> q;
  while (q--) {
    solve();
  }
}
