Is there any JavaScript library that can be used for calculations involving 700+ Digits? Also, how about the same thing in C++?
And then there is MAPM (Arbitrary Precision Math Library) in C with C++ bindings. I incooperated it some years ago for testing. Was very simple thanks to C++ bindings.
For C++ GMP has served me very well in the past for large numbers, it claims to be the fastest bignum library out there too, which is bound to be helpful for 700 digits.
For JS: How about BigInt?
For C++: Google found me this.