Defines even and odd numbers. Explains divisibility rules for 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 20, 25 and how to develop other divisibility rules. 70 problems solved in detail, with explanations. Includes a topic-specific glossary, index and lists of the first 600 prime numbers and prime factorizations of the first 300 natural numbers.