Lots of strange things are illegal in the U.S. — like playing cards on a Sunday in Alabama. So it should come as no surprise that there is such a thing as an illegal number. That's right: a number that no one in the United States can be in possession of.
What could make a number so dangerous it's been made illegal? The answer has to do with encryption. To prevent people from downloading copyrighted content directly from DVDs, companies started encrypting those media files. The illegal prime number is used to decrypt those digital copyright protections on DVDs.
In 1998, Congress passed the Digital Millennium Copyright Act to prevent people from bypassing technological protections aimed at preventing the illegal distribution of copyrighted materials like movies and music. Courts ruled that having possession of this number violated the DMCA.
Here's the full video from Wendell Productions:
Correction: May 4, 2016
A previous version of this article misstated the year Congress passed the Digital Millennium Copyright Act. The DMCA was passed in 1998.