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Sheldon Cooper's 73 Shirt: What Does it Mean?

Updated on May 6, 2012

So, you're wondering what the "73" on Sheldon's shirt meant if you watched the last episode of The Big Bang Theory, huh? Well, there's a little backstory to the significance of this number.  Well, it all started on season 4, episode 10's "The Alien Parasite Hypothesis".

Sheldon asks "What is the best number?  By the way, there is only one correct answer.... The best number is 73.  You're probably wondering why.  73 is the 21st prime number, it's mirror 37 is the 12th, its mirror 21 is the product of multiplying (hang on to your hats) 7 and 3.  Heh, heh, did I lie?"

Leonard says:  "Okay, so we get it.  73 is the Chuck Norris of numbers."

Sheldon replies:  "Chuck Norris wishes....  In binary 73 is a palindrome: 1-0-0-1-0-0-1, which backwards is 1-0-0-1-0-0-1... exactly the same.  All Chuck Norris backwards gets you is sirron kcuhc.

The 73 on Sheldon's shirt isn't just a random number...
The 73 on Sheldon's shirt isn't just a random number...

Sheldon's 73 Shirt

I love the Big Bang Theory, I watch it religiously. I've always loved Sheldon Cooper's t-shirts, in fact I like a lot of the shirts worn by all the characters. So much so that I wrote a hub on Sheldon Cooper T-Shirts. I've discovered I'm not the only one with a little geek in me, in fact.

Since the airing of the last episode called "The Thespian Catalyst", lots of people have been wondering where they can purchase Sheldon's 73 shirt. And, for those who missed "The Alien Parasite Hypothesis", they were curious about the significance of the "73" on Sheldon's shirt.

So, hopefully you've now got your answer. In true Sheldon form, it's of course an off the wall, completely nerdy play on numbers.

The Big Bang Theory Shuts Down Our Entire House Every Week

I kid you not... the phone isn't answered, the dog has to wait to go out and the kids must fend for themselves every Thursday night for 30 minutes.  There are a plethora of little subtleties you'd miss if you don't watch the show weekly.  The 73 shirt is a perfect example!  This is part of what makes the characters so rich and well developed.  Leave it to the writers and producers to think of having Sheldon wear this shirt... and without a mention of the meaning or significance.

Sheldon's 73 Shirt can be purchased on CafePress
Sheldon's 73 Shirt can be purchased on CafePress

Buy Sheldon's 73 Shirt!

His shirt is not easy to find... But, you can now purchase it on my CafePress store! To purchase any of my replicas of Sheldon's 73 shirts, Come visit my store on CafePress! There are a few different versions of the shirt there.

The first is the closest approximation to the shirt he wore on The Thespian Catalyst.

The second is just a different color scheme from the shirt he wore. It's white with a blue background instead of blue with a white background.

There's also a long sleeve shirt available. You should know, however, that Sheldon never wears just a long sleeve t-shirt. He has only and will only wear a short-sleeved t-shirt over a long sleeve t-shirt. But, I have a feeling he might forgive you if you break the rules a little. Or, maybe not...

The final shirt has Leonard's legendary quote: "73 is the Chuck Norris of numbers". Of course, Sheldon vehemently disagrees. This Sheldon 73 shirt is also available on my CafePress Store.


Submit a Comment
  • kilojuliett73 profile image


    7 years ago from Orem, Utah

    73 is a great number and one which both Jim Parsons and I share. We were both born in 1973 which makes the joke even more funny to those in the know.

  • Dr Zev profile image

    Joshua Zev Levin, Ph.D. 

    7 years ago from Marlton, NJ

    Albert Einstein was born on March 14 (Pi Day), the 73rd day of 1879. 1879 is a prime number, as is 5639, the year of Einstein's birth according to the Jewish Calendar.

    Another Chuck Lorre show, Two and a Half Men, features Jake Harper, whose birthday is also March 14.

  • profile image


    7 years ago

    73 is a ham radio term. It is used in morse code. It means "best regards" and is used because of the way it sounds in code which is...

    --... ...--

  • profile image


    7 years ago

    I love Bign Bang also. My wife and I also make sure to watch it. I have two shirts from Sheldon's collection. I have a Bazinga shirt with his picture on it and I have the rock, paper, scissors, lizard spock shirt.

    I was curious as to the meaning of the 73 shirt, (I forgot Sheldon's comments on the perfection of number 73) and that's how I found this page. I seem to recall he has also worn a number 42 shirt, which is a reference to "The Hitchhikers Guide to the Galaxy" by Douglas Adams.

  • SopranoRocks profile image


    8 years ago from Upper Peninsula, Michigan, USA

    The Big Bang Theory is the funniest comedy I have yet to see. Finally a show with intellectual humor instead of annoying mindless slapstick like many shows. I drop everything to watch and am happy there are so many reruns on TBS. I use to remind me when episodes I haven't seen are on tv. Plus I think Sheldon is one hot nerd. Everything he says has me LOL! Oh and CafePress has a huge variety of Big Bang items - I get lost in that site for hours; their inventory is massive and you can make your own t-shirt ideas to buy and sell (in the Design Your Own tab). Great HUB as always!

  • wordscribe43 profile imageAUTHOR

    Elsie Nelson 

    8 years ago from Pacific Northwest, USA

    It's a great show, isn't it Ginny? I love all the characters, Howard totally cracks me up. We've been watching re-runs non-stop these days. Just isn't even beginning to get old. Thanks for coming by everyone!

  • GinnyLee profile image


    8 years ago from Arlington, VA

    I love that show! I watch it on when I get home on Fridays. I am so glad the show was renewed for another season! Sheldon Cooper is a riot! Never did I think Nerds would be so popular.

  • Phil Plasma profile image

    Phil Plasma 

    8 years ago from Montreal, Quebec

    I like all of the characters for different reasons. I will admit that Sheldon can be the most entertaining, but even Raj has some moments where his humour wins out. Great hub, voted up and interesting.

  • Ebower profile image

    Erin Bower 

    9 years ago from Georgia

    I love that show. Great article! His shirts rock! lol

  • profile image


    9 years ago

    Haha, amazing. Never realized what the meaning behind '73' really was. The Big Bang Theory is definitely one of my favorite tv shows. I like the interaction and chemistry between the cast members and how robotic/psycho Sheldon is. I love it!

  • MPG Narratives profile image

    Maria Giunta 

    9 years ago from Sydney, Australia

    My family loves this show too so much so we watch repeat after repeat as well as the new ones. Sheldon is hilarious and I love the fact he is so Asperger like, so pedantic about things. The whole cast does a great job but Sheldon is definitely the stand out. Thanks for clearing up what the significance of the number 73 is too, wordscribe.

  • optimus grimlock profile image

    optimus grimlock 

    9 years ago

    Ive been watching it on and off since the begining and I agree sheldon makes the show!!!the jewish guys mom is funny as well reminds me of al's mother in law you never saw her just heard her.

  • ChrisLincoln profile image


    9 years ago from Orange (or Lemon...) County, California

    Of course there is also the fun of reading the vanity cards at the end of the program if you have the ability to pause your TV. A mini hub like no other. And, I believe the only opportunity to read a writers actual writing on prime time TV. Is it just a coincidence that Mr. Lorre's is also a Chuck? I think not...



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