C++ :

#include <iostream>
#include <cstdio>
using namespace std;

int main() {
	for (int i = 1000; i <= 10000; i ++) {
		int j = i%10*1000 + i/10%10*100 + i/100%10*10 + i /1000;
		if (i*(i/1000) == j) {
			cout << i << endl;
		}
	}

	return 0;
}

Pascal :

var
  a,b,c,i,s,k,m,j:integer;
begin
  for i:=1 to 9 do
   for j:=0 to 9 do
    for m:=0 to 9 do
     for k:=0 to 9 do
    begin
    if (i*1000+j*100+m*10+k)*i=k*1000+m*100+j*10+i then writeln(i,j,m,k);
    end;
end.