这可能算作作弊，但如果您使用 BigInteger，它有一个 IsEven 方法.

It may count as cheating, but if you use BigInteger, it has an IsEven method.

如MSDN所述，调用此方法相当于:

As stated in MSDN, calling this method is equivalent to:

value % 2 == 0;

参考:

• http://msdn.microsoft.com/en-us/library/system.numerics.biginteger.iseven(v=vs.110).aspx