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.
['q', '2461', '4603', '1147', '1995', 'H', 'H', '821', '2699', 'Q', '7383', '6841', 'x', 'Y', '2797', '531', '9813', '3827']