easiest way to calculate factorial of 2375?

Answer 1

are you trying to get its factors? then do want the other answer says
Are you trying to calculate factorital? 1x2x3 ...x2375?
Excell taps out at 300 factorial
I cannot take full credit for this answer but I found this info over a Google
as follows:
Subject: Re: Factorial for large numbers
Answered By: jeanluis-ga on 26 Jun 2002 15:39 PDT
Rated:
Hello,

83000! = 7.91222558e372239

Note: because you wanted it in exponential notation it is an
approximate value, the actual value would take a few thousand lines in
this message box, but I can post it if you want it, or you can do it
yourself with the instructions below.

To figure this out, I used an infinite precision math package written
for the Tcl scripting language called Mpexpr.

I had this already installed on my computer so I just wrote a small
program that computed this value, here is the program:
package require Mpexpr
set factorial [mpformat "%e" [mpexpr fact(83000)]]

And that is all there is to it (I say that as if it were nothing, but
in fact it took almost 30 minutes to compute the factorial and format
it on my computer). To run the factorial, assuming you have Tcl and
Mpexpr installed on your system (if you don't have them, I have
included instructions below), you would execute the main tcl (tclsh)
executable. It will give you a prompt that looks like this:
%

then you just type in those 2 lines above, and it computes the
factorial for you, and formats it in exponential notation.


If you don't have Tcl and Mpexpr installed on your system then you can
download them and install them from the following websites, they are
both freely available:

To get Tcl installed you should goto the Tcl website:
"Tcl 8.0"
http://www.scriptics.com/software/tcltk/8.0.html#Download Binary

Simply download the Windows Tcl self-extracting installer, and run the
tcl805.exe file. That should install Tcl.

To get the Mpexpr package installed do the following:
"Mpexpr download"
http://www.NeoSoft.com/tcl/ftparchive/sorted/math/Mpexpr-1.0/1.0/mpexpr-1.0.tar.gz

The once you download the Mpexpr package you can unzip it using any
zip utility (WinZip, PkZip, etc...) and then you should goto the
mpexpr-1.0\win directory, and read the README.win file, it will tell
you how to complete the install.

"Some information about Mpexpr"
http://www.nyx.net/%7Etpoindex/tcl.html#Mpexpr

Hope this works for you, feel free to ask for more info.

Answer 2

it ends in 5, so you know it's divisable by 5
which leaves you 475
again, by 5
95
again, by 5
19
19 is prime, so

2375 = 5^3 * 19

you need to know your multiplication here
there's no shortcut

if end number is even like 4728, or 9736390
it's divizible by 2

if sum of digits is divizable by 3, like 621 or 945, (6+2+1; 9+4+5) then it's divizible by 3

if divizible by 2 two times, then it's by 4

if last number is 5 or 0 like 8472965 or 39840, it's divizible by 5

.....