Assuming you are using jQuery UI 1.9+ (specify your version if not), you can retrieve your draggable div data to check if draggable is initialized using :
jQuery('.draggable1').data('ui-draggable');
Your click handler function will look like :
$('.draggable1').click(function() {
var $div = $(this);
if(!$div.data('ui-draggable'))
$div.draggable();
});
See it in action in this jsFiddle
Explanation : the jquery UI draggable widget is based on the jQuery UI widget factory and as described in the 'Instance' section of the documentation :
The widget's instance is stored using jQuery.data() with the widget's full name as the key.
You can also use the :data selector to check if your div element already has a draggable widget bound to it :
$div.is(':data(ui-draggable)');