11 185 272

11 185 272 is the number of decimal digits in the 46th known Mersenne prime, discovered on Sept. 6, 2008, by Hans-Michael Elvenich in Germany, a participant in the Great Internet Mersenne Prime Search.

A Mersenne prime has the form 2^p – 1, where p is a prime number. The 46th Mersenne prime, the second largest identified to date, is 2^37156667 – 1. A larger Mersenne prime, 2^43112609 – 1, was discovered on Aug. 23, 2008. The 46th Mersenne prime is the first prime to be discovered out of order since Walt Colquitt and Luther Welsh Jr. found 2¹¹⁰⁵⁰³ – 1 (the 29th Mersenne prime) in 1988.

Source: Great Internet Mersenne Prime Search; Mersenne Primes