Pure Silliness

[980iana]

Proof of F! = 1307674368000

F! = (1111)b! = (8 + 4 + 2 + 1)! = 15! = 15 * 14 * 13 * 12 * 11 * 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1 = 1307674368000
I saw a posting on a message board titled "F!" and I couldn't resist.