Psst ... What starts with "09f911", ends with "35688co", and has a whole lot of other numbers in between? Stumped? I'm afraid I can't tell you the answer, because that would be against the law.
You can have prime numbers, real numbers, imaginary numbers, irrational numbers, and, ever since the movie industry decided to wage war on the internet, you can also have illegal numbers. It all started in 1999 when a Norwegian hacker called Jon Johansen created DeCSS, a program that unravelled the "content scrambling system" intended to limit the kinds of machines on which DVDs could be played, so that he could watch them on his Linux computer.
As the DeCSS code began to circulate among other Linux users, a coding zine, 2600: the hacker quarterly, picked up the story and linked to the code online. Thanks to the Digital Millennium Copyright Act (DMCA)--the then nascent US law that renders illegal the circulation of such copyright circumvention tools--this was enough to get the magazine taken to court by the DVD Copy Control Association. Hackers worldwide were outraged, and began to protest the only way they knew how--by wearing T-shirts.
Except that these T-shirts, which had the program code written on them in full, were designed to make a point about free speech. You can't make numbers illegal, was the message: what are you going to do--throw me in jail for wearing a T-shirt? And it wasn't …