...

386! = 300 2665366520 8755582903 3345000063 0933184096 3550392751 1664147182 0499734725 8296126846 5252516059 9730397713 6252641384 5705669545 1577926013 1893735727 4065594295 4866195550 0233594014 1755020797 2844581987 7971506520 8866445606 3529812510 5856946586 3222721808 4121192521 5135767764 3686166365 8503648896 5559254328 3996428349 7349348049 1331159927 0875024868 6527579059 3419975694 0012558821 7002911036 2048989780 4985303473 6850964460 3348329817 4632206323 9807745300 6125177810 2438021524 4451216066 6763938734 9877224771 2704913550 1839059825 8287209819 2708586029 1680960180 6857568765 4265894797 4099940060 0414826937 0397070910 6242919910 2694366291 7872935014 6346432168 1045878558 9853876791 7170874046 9523706315 0045348787 4232848718 4228390421 8581564848 1526066812 2293859261 6579736545 5257600000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 =833 digits long.

If you don't require the FULL computation, you can use "Stirling's Approximation Formula":

S =n! ~ sqrt(2.pi.n) * (n/e)^n =Sqrt(2 x 3.141592 x 386) x (386 / 2.718281828)^386 = 

3.0020171928170054524994166439502 x 10^832