Progress Bar not progressing

I am doing a prime tester application and i want to show the progress of the testing while taking place. Here is my code when i run it on my phone i don't see the progress bar horizontal filling it just stays there.

public class MainActivity extends Activity{

//My global Views
Button b;
TextView tv;
EditText et;
int alaa;
ProgressBar pb;
long dv;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //The References
    b  = (Button)      findViewById(R.id.bt);
    tv = (TextView)    findViewById(R.id.tv);
    pb = (ProgressBar) findViewById(R.id.progressBar1);
    et = (EditText)    findViewById(R.id.et);


b.setOnClickListener( new View.OnClickListener() {


//CALCULATE INPUT   
public void onClick(View v) {
    if(et.getText().toString().isEmpty()){
        tv.setText("Please Insert a Number!");
    }else{
    int etll = Integer.parseInt(et.getText().toString());
    Long etl = Long.parseLong(et.getText().toString());
    long a=0;
    int torf = 0;
    pb.setMax(etll);
    int alaa = 0;
    long etlt = etl/2 + 1;
    for(a=2;a<etlt;a++){
        if(alaa > etll){
        setProgress(alaa);
        alaa++;
        }
        if(etl%a == 0){
            torf = 1;
            dv = a; 
            break;
        }
    }