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Understanding Prime Numbers

Introduction

A Prime Number is a number that cannot be evenly divided by any other whole number other than 1 and itself. So 1, 2, 3 and 5 are all prime numbers, but 4 is not, since 4 can not only be divided by 1 and 4, but 2 as well.

Terms

Prime Number - A prime number is a number that cannot be evenly divided by any number other than 1 and itself.

Lesson

A prime number is a number that is not evenly divisible by any number other than 1 or itself. So if we are asked to list all the prime numbers between 1 and 10, we could determine the answer by considering each number between 1 and 10, and determining whether it has any factors other than 1 and itself.

NumberFactors
11
21, 2
31, 3
41, 2, 4
51, 5
61, 2, 3, 6
71, 7
81, 2, 4, 8
91, 3, 3, 9
101, 2, 5, 10

Essentially, any number that has an entry in the 'Other Factors' column is not a prime factor. So the prime numbers between 1 and 10 are 1, 2, 3, 5 and 7.

(Fun Fact: Did you know that '2' is the only even prime number?)

Examples

Picking Prime Numbers

Which of the whole numbers are prime numbers?
The factors of are . Therefore is a prime number.
The factors of are . Therefore is not a prime number.
The factors of are . Therefore is not a prime number.
The factors of are . Therefore is a prime number.

Listing Prime Numbers

List All Prime Numbers Between
List prime numbers between and
are the prime numbers between and

Picking Prime Numbers

Which of the whole numbers are prime numbers?
The factors of are . Therefore is not a prime number.
The factors of are . Therefore is a prime number.
The factors of are . Therefore is not a prime number.
The factors of are . Therefore is a prime number.

Listing Prime Numbers

List All Prime Numbers Between
List prime numbers between and
are the prime numbers between and

Picking Prime Numbers

Which of the whole numbers are prime numbers?
The factors of are . Therefore is not a prime number.
The factors of are . Therefore is a prime number.
The factors of are . Therefore is a prime number.
The factors of are . Therefore is not a prime number.