I\'m reviving this question, and making it more specific: Is there a .NET framework library that supports numbers with arbitrary digits of precision?
GnuMpDotNet: http://www.emilstefanov.net/Projects/GnuMpDotNet/
If you need pure .NET consider looking into this: http://www.codeplex.com/IntX/
If you want a really fast library then try:
http://www.emilstefanov.net/Projects/GnuMpDotNet/
There are a few options here.
A good option is W3b.Sine, which is native C#/.NET, and supports arbitrary precision floating point values.
If you are only dealing with integer values, IntX provides support for arbitrary precision integer values. A potentially more mature option would be C# BigInt, but again, this will not support floating point operations.
Can you wait for .NET 4.0? They're bringing BigInteger directly into the Framework.
On the other hand, if you can't wait, then the J# runtime includes built-in support for java.math.BigInteger and BigDecimal. This is redistributable just like the rest of the .NET Framework.
Here is a good article on how to represent infinite digits.
http://dobbscodetalk.com/index.php?option=com_myblog&show=Basic-Arithmetic-with-Infinite-Integers.html&Itemid=29
good luck
Perhaps surprisingly, the Bailey-Borwein-Plouffe formula gives an incremental procedure for computing the next binary or hexadecimal digit of pi without needing to store all the previous digits.