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.
['3369', 'X', 'G', '7137', 'm', 'a', '1819', 'H', 'c', 'L', '1847', 'o', '5879', '403', '2281', 'N', 'C', 'V', '9619', '6059']