CREATE TABLE table_21324 ("Rank" FLOAT, "1-year peak" TEXT, "5-year peak" TEXT, "10-year peak" TEXT, "15-year peak" TEXT, "20-year peak" TEXT)

What is the highest rank when Anatoly Karpov, 2820 is the 15-year peak?
SELECT MAX("Rank") FROM table_21324 WHERE "15-year peak" = 'Anatoly Karpov, 2820'
SELECT MAX("Rank") FROM "table_21324" WHERE "15-year peak" = 'Anatoly Karpov, 2820'