Is it there or is not?
The answer was true for beta 1 build of netfx 3.5. It is true if you can manage to run under full trust for beta2 and RTM versions, because then, you can use reflection to create an instance of BigInteger and invoke members.
This value type supports +, -, –, ++, /, ==, >=, >, !=, <, <=, %, *, -, + as supported arithmetic operators.
For functions, it has Abs, Add, Compare, CompareTo (overloaded), Divide, DivRem, GreatestCommonDivisor, ModPow, Multiply, Negate, Parse (overloaded), Pow, Remainder, Subtract, ToByteArray (overloaded), ToString (overloaded) and TryParse (overloaded) to offer. Note, Add, Divide, Multiply, Negate, Remainder and Subtract actually implement functionality for corresponding operators.
There are also a host of convert-from and convert-to operators, performing conversions to and from all built-in numeric data types.