Compose extremely large integers using BigInteger in C# .NET

The largest integer that can be stored in a long, i.e. a 64-bit integer is 9,223,372,036,854,775,807 in .NET. That is a very large number that will be enough for most applications out there.

However, sometimes it’s not enough and you need to handle something larger. This article on Wikipedia shows several use cases where this can occur. .NET also provides the float and double numeric types that provide much larger ranges. They won’t be integers exactly but they may suit your needs anyhow.

The .NET framework has an object called BigInteger that lets you construct arbitrarily large integers. This object resides in the System.Numerics namespace so you’ll need to reference the System.Numerics.dll library.

E.g. googol is equal to 10 raised to the power 100. Here’s how you can construct that number:

BigInteger googol = BigInteger.Pow(10, 100);

One googol is 1 followed by 100 zeroes:

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

BigInteger has a static Parse method which works the same way as Parse of other numeric types:

string googolString = googol.ToString();
BigInteger backToGoogol = BigInteger.Parse(googolString);

Otherwise BigInteger behaves much the same way as other numeric types: you can find the min and max values, multiply and divide them etc.

View all various C# language feature related posts here.