An illegal prime is a prime number that represents information that it is forbidden to possess or distribute. One of the first illegal primes was discovered in 2001. When interpreted in a particular way, it describes a computer program that bypasses the digital rights management scheme used on DVDs. Distribution of such a program in the United States is illegal under the Digital Millennium Copyright Act.^[1] An illegal prime is a kind of illegal number.

(and don’t even get me started on the binary representation of Pi)