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B. Prime and Composite Numbers

Information technology uses prime numbers to create sub-routines in cryptography. Cryptography is the practice of securing communication through the use of prime number algorithms. Some natural numbers greater than 1 can be classified as prime numbers.

 Prime Numbers
numbers with exactly two factors, 1 and itself

Natural Numbers
counting numbers, such as 1, 2, 3, ...

For instance, the number 3 has factors of 1 and 3 (itself) only. As such, 3 is a prime number.

But, what if a number has factors other than 1 and itself?

Numbers with factors other than 1 and itself are classified as composite numbers.

Composite Numbers
numbers with more than two factors (In other words, more factors than just 1 and itself. A composite number can be written as the product of two factors, neither of which is itself.)


For instance, the number 4 is a composite number because 4 has more factors than just 1 and itself.

The number 4 has factors of 1, 2, and 4.

By definition, the number 1 is neither prime, nor composite. It does not have exactly two factors, nor does it have more than 2 factors. The number 1 has only one unique factor, 1.

Consider the number 0. Would 0 be considered prime, composite, or neither?