libtommath-dev binary package in Ubuntu Focal amd64

 LibTomMath is a C language library that provides a vast array of highly
 optimized functions for number theory; including:
 .
  * Simple Algebra (Addition, Subtraction, Multiplication, Division)
  * Digit Manipulation (shift, binary AND/OR/XOR)
  * Modular Reduction (Barrett, Montgomery, DR, 2k)
  * Number Theory
    - Greatest Common Divisor
    - Least Common Multiple
    - Jacobi Symbol Computation
    - Multiplicative Inverse
    - Modular Exponentiation
    - Fermat & Miller-Rabin Primality Tests
  * Miscellaneous
    - Root finding over Z
    - Pseudo-random integers
    - Signed & Unsigned comparisons
    - Karatsuba and Toom-Cook multiplication algorithms
    - Fast Comba based Multiplier, Squaring and Montgomery routines
 .
 This package contains the files needed to create programs that use LibTomMath.
 It is not needed to merely execute programs that use LibTomMath.

Source package