For the event which happened at 14:09:49 on 2016/5/6, in the location coordinate(116, 40), how many apps were active?
at 14:09:49 on 2016/5/6 refers to timestamp = '2016/5/6 14:09:49'; location coordinate(116, 40) refers to longitude = '116' AND latitude = '40'; active refers to is_active = '1';
SELECT COUNT(T1.app_id) FROM app_events AS T1 INNER JOIN events AS T2 ON T1.event_id = T2.event_id WHERE T2.timestamp = '2016-05-06 14:09:49' AND T1.is_active = '1' AND T2.longitude = '116' AND T2.latitude = '40'