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_64542 ( "No. in series" real, "No. in season" real, "Title" text, "Directed by" text, "Written by" text, "Original air date" text, "Ratings" text )

### Question ###
What is the sum of the numbers in series written by sam meikle, which have 21 numbers in the season?

### Accurate SQL ###

SELECT SUM("No. in series") FROM table_64542 WHERE "Written by" = 'sam meikle' AND "No. in season" = '21'