Factors, multiples, divisibility rules, and number sense all come together in this 4th grade and 5th grade math mystery number puzzle resource. Number Hacker - Identify the Mystery Number includes 291 printable number riddle worksheets that give students meaningful practice with factors, multiples, divisibility, remainders, prime and composite numbers, even and odd numbers, place value, digit sums, and logical reasoning. Students read each set of clues, eliminate possible answers, and identify