K-12 Assessment Center, Inc.

Definitions

Numbers

Whole numbers – numbers that do not have a decimal or fraction part.

Include the number ‘0’. We wouldn’t leave you out!

Examples: 0, 1, 2, 3, 21, 106, 1,456, 755,892, etc.

Counting Numbers – whole numbers starting with the number 1.

Does not include the number ‘0’. Sorry.

Examples: 1,2,3,4,5,6, etc.

Factors of a number – if a number can be evenly divided by another number, that other number is called a factor of the first number.

Example: 14 can be divided by 2 and 7. 2and 7 are factors of 14. So are 1 and 14. (Note: ‘evenly divided’ means, there is no remainder when you divide.)

Prime and Composite Numbers

A prime number is a whole number that only has two factors which are:

The whole number itself and the number 1.

A composite number has factors in addition to 1 and itself.

The numbers 0 and 1 are neither prime nor composite. Sorry again.

All even numbers are divisible by two and so all even numbers greater than two are composite numbers.

All numbers that end in five are divisible by five. Therefore all numbers that end with five and are greater than five are composite numbers.

The prime numbers between 2 and 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.

Divisibility Rules

2	All even numbers are divisible by 2
3	If the sum of the digits is divisible by three, the number is also divisible by 3
5	If the last digit is a 5 or a 0, the number is divisible by 5.
6	If the number is divisible by both 3 and 2, it is also divisible by 6.
9	If the sum of the digits is divisible by 9, the number is also. *This holds for any power of 3
10	If the number ends in 0, it is divisible by 10.