CREATE TABLE table_29631 ("#" FLOAT, "No." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Viewers" FLOAT, "Original airdate" TEXT, "Prod. code" FLOAT)

How many people watched episode number 13?
SELECT "Viewers" FROM table_29631 WHERE "#" = '13'
SELECT "Viewers" FROM "table_29631" WHERE "#" = '13'