What's Your Number? Overview

After reading a magazine article that says the average woman sleeps with 10.5 men, Ally Darling (Anna Faris) starts counting what number she's up to and realizes with shock that she's slept with 19 men. She decides that if she gets to number 20, she'll have to marry him. So with the aid of her womanizing neighbor Colin (Chris Evans), Ally decides to find her ex-boyfriends in the hopes of finding the man of her dreams.