Prime & Composite Numbers

• A prime number has only two factors, 1 and itself.

• A composite number has more than two factors.

• “1” is a special case. It is neither prime nor composite since it has only one factor, which is 1.

• “2” is the only even prime number. All other even numbers are divisible by 2, so all other even numbers are composite.

Let’s find the prime numbers from 1 – 100…

• Put a box around “1” because it is neither prime nor composite

• Circle “2.” It is the first prime number. Now cross out all multiples of 2.

• Circle “3.” It the next prime number. Cross out all multiples of 3.

• Circle “5.” It is the next prime number. Cross out all multiples of 5.

• Circle “7.” It is the next prime number. Cross out all multiples of 7.

• Highlight all numbers circled or not crossed out – these are the PRIME numbers from 1 – 100.

There should be twenty-five prime numbers.

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