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.
['Z', '4531', 'J', 's', 'F', 'i', '8895', '9903', '1587', 'r', '2187', '1845', '2153', '1745', 'j', 'c', 'N', 'F', 'U', 'k']