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_72177 ( "District" text, "Vacator" text, "Reason for change" text, "Successor" text, "Date successor seated" text )

### Question ###
Who was the vacator when the date successor seated was august 21, 1973?

### Accurate SQL ###

SELECT "Vacator" FROM table_72177 WHERE "Date successor seated" = 'August 21, 1973'