CREATE TABLE table_23157997_13 (mountains_classification VARCHAR, youth_classification VARCHAR)
SELECT COUNT(mountains_classification) FROM table_23157997_13 WHERE youth_classification = "Mike Northey"
มี Mountains Classifications กี่รายการในการแข่งขันกับ Mike Northey ในฐานะ Youth Classification
How many Mountains Classifications were in the race with Mike Northey as Youth Classification?