primecount is a command-line program and C/C++ library that counts the primes below an integer x ≤ 10^31 using highly optimized implementations of the combinatorial prime counting algorithms.

primesieve is a command-line program and C/C++ library that generates primes using a highly optimized sieve of Eratosthenes implementation. primesieve can generate primes and prime k-tuplets up to 2^64.