The following is an incomplete list of some arbitrary-precision arithmetic libraries for C++.
GMPThe GNU Multiple Precision Arithmetic Library MPFRThe GNU MPFR Library MPIRMPIR Multiple Precision Integers and Rationals TTMathBignum C++ library Arbitrary Precision Math C++ PackageArbitrary precision package Class Library for Numbers Number Theory Library ApfloatApfloat Home Page C++ Big Integer LibraryC++ Big Integer Library MAPMMAPM Home Page ARPRECHigh-Precision Software Directory InfIntInfInt Universal NumbersC++ Template library for arbitrary precision posits and valids mp++C++11/14/17/20 library for multiprecision arithmetic num7C++ ARBITRARY PRECISION ARITHMETIC-LOGIC DECIMAL LIBRARY slimcpplibSimple long integer math library for C++ Footnotes
References