University of California, San Diego: Edward Bender and S. Williamson's "Arithmetic, Logic and Numbers: Number Theory"
Read Section 1 beginning at "Prime Numbers and Factorization" on page NT-3, and continue up to example 3 on page NT-4. Example 3 also applies to 3.1.4 and 3.2.2 below. Prime numbers are the next set of commonly used numbers to be introduced. The introduction of prime numbers leads to the discussion of factoring an integer.