n C r denotes the number of combinations of n things taking r at a time.

661.

Not as elegant as K.S.'s but it follows that 2000!/(1000! * 1000!) is

 (2000 * 1999 * 1998 * . . . * 1001 )

     (1000 * 999 * 998 * . . . *1)

All the numbers between 1001 and 2000 that are divisible by 2 can be tossed. This leaves numbers between 1001 and 2000 that are divisible by 3 (666, 665, 664 . . .). The highest prime in this set is 661.

Edited on May 12, 2006, 12:45 pm

Posted by Leming on 2006-05-12 12:37:31