7 (seven) is a prime number.
SESAME STREET MENTIONS
The Alligator King
The Count's Number Of The Day #7 - Seven chickens appear.
Number Creatures - 7 is a pelican.
Seven colorful friends form a 7.
Falling Baker #7 - 7 straws, 7 circles, 7 ducks, 7 spiders, 7 nickels, 7 pumpkin pies
In Sammy The Snake, "seven" is one of the S words mentioned.
Fem Myror Cartoons - 7 owls, 7 piglets, 7 rabbits, 7 starfish, 7 walruses
Pinball #7 - Around The World
Elmo sings Seven Goldfish.
Far From Seven
An Anything Muppet girl counts 7 of what she thinks they are fence posts, but they're actually a monster's teeth.
Seven Sweet Sporanos
Mad Painter tries to paint a 7, but sees a 7 on a football jersey.
Have a 7 and a smile
The Count counts 7 flowers and sneezes 7 times.
The Magnificent Seven