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_21 ( silver INTEGER, bronze VARCHAR, total VARCHAR, nation VARCHAR )

### Question ###
What is the sum of all silver medals with less than 23 medals in total and more than 3 bronze medals for the United States?

### Accurate SQL ###

SELECT SUM(silver) FROM table_name_21 WHERE total < 23 AND nation = "united states" AND bronze > 3