


Prime Factors, HCF and LCMPrime NumbersA number p is a prime if it has exactly two factors; namely 1 and p. In other words, the only factors of a prime are the trivial factor and the improper factor. A number that has a nontrivial proper factor is said to be composite. The number 1, therefore, is neither a prime nor a composite. All other numbers which are not prime are composite. The number 2 is the smallest prime. Examples6 is composite, as 6 = 2×3. The numbers 2 and 3 are nontrivial proper factors of 6. The numbers 2, 3, 5 and 7 are prime. Let's look at a good method for discovering small primes: Eratosthenes’s Sieve MethodSuppose we are trying to discover all prime numbers ≤ M.
We demonstrate the process with numbers less than 50. Exercise
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