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.
['p', '5815', 'm', '6551', '2807', 'k', '3745', 'o', 'B', 'H', '6201', 'f', '3631', 'O', '9385', '9783', 'D', '679', '2587']