Getting the number pad to show up for text fields
hook_field_widget_form_alter


  Alter forms for field widgets provided by other modules.


or use hook_field_widget_WIDGET_TYPE_form_alter to hook into the Number field specifically.

/**
 * Implements hook_field_widget_WIDGET_TYPE_form_alter().
 */
function mymodule_field_widget_number_form_alter(&amp;$element, &amp;$form_state, $context) {
  $element['#type'] 'number';
}