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.
['r', 'n', 'Y', '2281', 'v', '9483', 'n', 'y', 'V', '2547', 'p', 'G', '7383', '2709', 'O', '1961', '1521', '1051', '9477', 'X']