| Positive integers other than primes, known as composite numbers, can be written as the product of smaller primes. |
| In other words, a number is rational if we can write it as a fraction where the numerator and denominator are both integers. |
| A second work is the Book of the Number which describes the decimal system for integers with place values from left to right. |
| By contrast, which is sometimes overlooked, in the arithmetical Books 7-9 multiplication of integers themselves occurs as usual. |
| Positive integers greater than 1 that aren't prime are called composite integers. |
| Possibly as a consequence of that, the Greek mathematicians thought of fractions in terms of ratios of integers, rather than numbers. |
