which was factored by Brent & Morain in 1988. was factored by A.K. Lenstra, H.W. Lenstra Jr., M.S. Manasse & J.M. Pollard in 1990. was factored by Richard Brent who found a 40-digit factor of on October 20, 1995. The cofactor is a 252 digit number, which is not so easy to factor. Luckily, this number was also prime.