When the production (mt) is 650000, what is the total number of rank?
CREATE TABLE "table1_21109892_1" (
  "rank" real,
  "commodity" text,
  "value_int_1000" real,
  "production_mt" real,
  "quantity_world_rank" text,
  "value_world_rank" text
);
SELECT COUNT("rank") FROM "table1_21109892_1" WHERE "production_mt"=650000;