This is a very simple application that calculates all the prime numbers between 2 (The lowest prime) and the number you provide.
The "Sieve of Eratosthenes" process is used for the most efficient way I could find (look it up).
The Sieve of Eratosthenes is an ancient, efficient algorithm for finding all prime numbers up to a specified limit by iteratively marking off multiples of each prime, starting with 2, as composite (non-prime) until only prime numbers remain. It works by creating a list of numbers, identifying the first prime (2), then crossing out all its multiples (4, 6, 8...), moving to the next unmarked number (3), marking out its multiples (6, 9, 12...), and continuing this process up to the square root of the limit, leaving the unmarked numbers as primes.