$(document).ready(function(){
  $("#numero").keyup(function(){
    var myVal = $(this).val();
    var valid = "0123456789";

    for (var i=0; i < myVal.length; i++) {
      temp = "" + myVal.substring(i, i+1);
      if (valid.indexOf(temp) == "-1")
        myVal = str_replace(temp, "", myVal);
    }

    $(this).val(myVal);
  });

function str_replace(a, b, str) {
  return str_replace2(str, a, b);
}
function str_replace2(SRs, SRt, SRu) {
  SRRi = SRs.indexOf(SRt);
  SRRr = '';
  if (SRRi == -1) return SRs;
  SRRr += SRs.substring(0,SRRi) + SRu;
  if ( SRRi + SRt.length < SRs.length)
    SRRr += str_replace2(SRs.substring(SRRi + SRt.length, SRs.length), SRt, SRu);
  return SRRr;
}
});