Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21716139_1 (frequency VARCHAR, train_no VARCHAR)

### Question ###
What is the frequency of trains numbered 12671/12672?

### Accurate SQL ###

SELECT frequency FROM table_21716139_1 WHERE train_no = "12671/12672"