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.
['7829', 'Y', 'W', 'M', 't', '3571', 'W', 'M', '8793', '3359', 'C', 'i', '9589', '447', '4449', '1733', 'o', 'h', 'e', '1647']