Here is the factorial! calculator itself:  https://www.wolframalpha.com/

100! = 933262154439441526

816992388562667004907159

682643816214685929638952

175999932299156089414639

761565182862536979208272

237582511852109168640000

00000000000000000000

171! = 124101807021766782342484

052410310399261660557750169318

538895180361199607522169175299

275197812048758557646495950167

038705280988985869071076733124

203221848436431047357788996854

827829075454156196485215346831

804429323959817369689965723590

394761615227855818006117636510

842880000000000000000000000000

0000000000000000

250! = 3232856260909107732320814552024

3684709948437176737806667479424271128

2374755511120948881791537102819945092

8507353189432926730931712808990822791

0302790712819216765272401892647332180

4118626100683292536513367893908956993

5713530175040513178760077247933065402

3390061648255522488194365725860573992

2264125483298220484913772177665064127

6858807153128978777672951913990844377

4787025891729732551502832417873206581

8848206247858265980884882554880000000

0000000000000000000000000000000000000

000000000000000000

Factorial is the product of an integer and all the integers below it;

The factorial 5! is equal to:

5! = 5 X 4 X 3 X 2 X 1 = 120

The factorial 4! is equal to:

4! = 4 X 3 X 2 X 1 = 24

... and the 0! = 1 🙂

Your numbers are big, so I suggest using special calculator(s) for finding them! For example:

25! = 15,511,210,043,330,985,984,000,000

So you can imagine...

You can easily use your PC's (for Windows) calculator. From the "View" menu choose "Scientific" option and use the n! option; BUT bear in mind that you will NOT see all the numbers like on the other calculators!

Here is the code for C# - BUT you must use BigInteger - and using System.Numerics; (in References):

using System;
using System.Numerics;
 
class FindFactorialWhileLoop
{
    static void Main()
    {
        {
            Console.Write("Enter your factorial number = ");
            int n = int.Parse(Console.ReadLine());
            BigInteger factorial = 1;
 
            while (true)
            {
                Console.Write(n);
                if (n == 1)
                {
                    break;
                }
                Console.Write(" * ");
                factorial *= n;
                n--;
            }
            Console.WriteLine(" = {0}", factorial);
        }
    }
}