Skill: Identify composite numbers

A composite number is a whole number greater than $1$ that has more than two positive factors. In other words, it has a factor pair besides $1$ and the number itself.

To identify a composite number:

1. Check that the number is greater than $1$.
2. Look for a factor pair other than $1$ and the number.
3. If you find one, the number is composite.
4. If no other factor pair exists, the number is prime.

Remember:

• $0$ and $1$ are neither prime nor composite.
• A prime number has exactly two positive factors: $1$ and itself.

Example: Is $24$ composite?

Find factor pairs for $24$:

$$1 \times 24 = 24$$

Now look for another pair:

$$2 \times 12 = 24$$

Because $2$ and $12$ are factors of $24$, $24$ has a factor pair besides $1$ and $24$. It has more than two positive factors, such as $1$, $2$, $3$, $4$, $6$, $8$, $12$, and $24$.

Therefore, $24$ is composite.