In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['5333', '5781', '5307', '809', '5875', '9273', '7655', '4297', '5119', 'w', '8605', 'H', '2853', '7455', '1163', '6459', '6625', 'U', 'z', '5773']