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_name_64 (format VARCHAR, year VARCHAR, catalog_number VARCHAR)

### Question ###
What format is after 1991 and has a Catalog Number of 81868?

### Accurate SQL ###

SELECT format FROM table_name_64 WHERE year > 1991 AND catalog_number = "81868"