Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter R - Section R.1 - Factors and the Least Common Multiple - Exercise Set - Page R-6: 12

Answer

Composite number

Work Step by Step

A $\textit{prime}$ number is a natural number greater than $1$ which has only two factors: $1$ and the number itself. In case it has more than two factors, it is a $\textit{composite}$ number. In order to determine if the given number is prime, we determine its factors. $21=1\cdot 21=3\cdot 7$. Because $21$ is divisible by $1$, $3$, $7$ and $21$, therefore by more that $1$ and itself, it follows that it is a composite number.
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