Factorizer may be used: (1) to get the prime decomposition of all numbers in a range of numbers, (2) to get all factors of a single number or all factors of all numbers in a range, (3) to find only the prime numbers in a range of numbers, (4) to find pairs of prime numbers in a certain range, (5) to count (without displaying) the prime numbers in a range of numbers and (6) to find Fermat and Mersenne primes less than 2,147,483,647.