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_21716139_1 (category VARCHAR, train_no VARCHAR)
### Question:
What is the category for trains numbered 16609/16610?
### Answer:
SELECT category FROM table_21716139_1 WHERE train_no = "16609/16610"