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_21324 ( "Rank" real, "1-year peak" text, "5-year peak" text, "10-year peak" text, "15-year peak" text, "20-year peak" text )

### Question ###
What is the highest rank when Anatoly Karpov, 2820 is the 15-year peak?

### Accurate SQL ###

SELECT MAX("Rank") FROM table_21324 WHERE "15-year peak" = 'Anatoly Karpov, 2820'