The number 10 has two even factors, 2 and 10; and two odd factors, 1 and 5. The number 12 has four even factors, 2, 4, 6, and 12; and two odd factors, 1 and 3. Find numbers whose factors are all even (except, of course, for the odd number 1). What do you notice about these numbers?
(Source: Mathematics Teaching in the Middle School, Nov-Dec 1997)
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