It can multiply two numbers written as strings.
It works base 10 by string indexing, it is not the fastest.
The next slowest down is pen and paper.
GMP is my favourite external big number library.
It is probably the fastest one around.
It is written in C of course, and is very portable.
These ancient languages, Pascal, C, C++, Fortran and Basic tend not to have a built in big number library, but I think Lisp does a switch over.
I think a few of the functional languages include one.
Also
Python does, but it would, wouldn't it?