Dirichlet is an opensource number theory library for .NET.
Much more is coming but the initial release provides high-performance 128 bit signed and unsigned data types. Who needs 128 bit integers? If 64 bit numbers are too small but BigInteger is too slow, then these data types are for you.
If you want to see the parent project that this came from, see Dirichlet.
This a forked version for Unity Package Manager compatibility.
Info .NET Version of 7+ Has their own built in Int128