Primes or prime numbers are whole number values that have but two factors which are itself and one. Any value that has factors beside one and itself is classified as a composite number. There are two integers that do not match either of these groupings and that is zero and one. Since all even numbers are divisible by two, every value that is even and greater than two is a composite number. Also, all numbers that end in five are divisible by five, so any value greater than five that ends in a five is a composite number as well. We use these classifications to understand the significance of a value. Prime numbers act as the building blocks for all other numbers because composites are just primes that are multiplied together. We share with students the three-steps we can take to check if an integer is prime or composite. We start by identifying the square root of the number, calculators are acceptable for this. Your next step is to determine all the primes of the integer (of the square root). The last step is to divide your original number by all of the primes that you just have identified.
This section really helps you classify integers quickly. These worksheets explain how to determine whether or not a number is prime or composite and how to find the prime numbers within a given range of numbers.