Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_23157997_13 (mountains_classification VARCHAR, youth_classification VARCHAR)
### Question:
How many Mountains Classifications were in the race with Mike Northey as Youth Classification?
### Answer:
SELECT COUNT(mountains_classification) FROM table_23157997_13 WHERE youth_classification = "Mike Northey"