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_19 ( frequency_mhz VARCHAR, call_sign VARCHAR, erp_w VARCHAR )

### Question ###
What is the total frequency mhz of the kgrj call sign, which has an erp w greater than 21,500?

### Accurate SQL ###

SELECT COUNT(frequency_mhz) FROM table_name_19 WHERE call_sign = "kgrj" AND erp_w > 21 OFFSET 500