# What is a prime number? | Summary and Q&A

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March 25, 2020
by
tecmath
What is a prime number?

## TL;DR

Prime numbers have only two factors (1 and itself), while composite numbers have more than two factors.

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### Q: What is a prime number?

A prime number is a counting number with exactly two factors, itself and one. Examples of prime numbers include 3, 7, and 2.

### Q: What are composite numbers?

Composite numbers are counting numbers with more than two factors. Examples are 6 and 15, which have factors other than 1 and themselves.

### Q: Why is 2 a special prime number?

2 is a special prime number because it is the only even prime number. It only has two factors, 2 and 1.

### Q: How can we determine if a number is composite?

Apart from being an even number that is not 2, a good clue to identify composite numbers is if the number ends in a 5 or 0, but is not 5. Most numbers divisible by 5 will have these endings.

## Summary & Key Takeaways

• Prime numbers are counting numbers with only two factors, themselves, and one.

• Examples of prime numbers are 3, 7, and 2 (which is the only even prime number).

• Composite numbers have more than two factors, such as 6 and 15.