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_2417340_3 (vacator VARCHAR, date_of_successors_formal_installation VARCHAR)

### Question ###
List the number of vacators when successors were formally installed on June 22, 1868.

### Accurate SQL ###

SELECT COUNT(vacator) FROM table_2417340_3 WHERE date_of_successors_formal_installation = "June 22, 1868"