POST数据未存储

I am trying to use Ajax to send information over to a PHP script to store that information. But when I test it, the data stored at the php side is empty instead of 1234. Can I know what I'm doing wrong please.

//Javascript/ Ajax
document.getElementById('Btn1').onclick = function () {
    var num = 1234;
    updater(num);
};

function updater(number){
    $.ajax({
        type: "POST",
        url: "http://www.example.com/updt.php",
        data: number,
        error: function (jqXHR, textStatus, errorThrown) {
            alert(" server " + textStatus + ":" + errorThrown)
        },
        success: function (data) {
            alert(data);
        }
    });
}

//PHP
$myData = $_POST["data"];
echo $myData . "empty.."; //echoes empty.. instead of 1234empty..

Post your data like this

data: {'data':number}, // object

or like this

data:'data='+number // name value pair

instead of

data: number,