We’ve received our share of intriguing questions over the years, but this one takes the cake. On Monday, a correspondent called from National Public Radio to discuss the implications of typesetting a number with twelve million digits.
The number in question is 243112609-1, which holds the title for World’s Largest Known Prime Number. Mathematicians have known since at least the third century BC that for many values of n, the formula 2n-1 produces a prime number. When it does, the result Mn is called a Mersenne Prime, after the seventeenth century French mathematician who calculated the first 257 of them by hand — quite something when you realize that M257 has 78 digits. (And, so very cruelly, it’s not prime.) The search for prime numbers, an esoteric pursuit that rivals typeface design for its cultishness, has continued ever since; these days it’s assisted by the Great Internet Mersenne Prime Search, a project that organizes the downtime of almost 90,000 volunteers’ computers into a collective effort to find the next great prime.