Show:
Odd & Even Numbers
Prime Numbers
Composite Numbers
Factors
Multiples
100

What is an odd number?

  1. A number that is not divisible by 2.
  2. Cannot be in pairs.
100

What is a prime number?

What is the smallest prime number?

A number that has exactly two factors — 1 and itself.

2

100

What is the smallest composite number?

Is 4 a composite number?




4

Yes, because it has factors 1, 2, and 4.


100

Name the two factors that every number has.


  1.  1 and the number itself.
  2. EX: 3 = 1 and 3
  3.       12 = 1 , 2 , 3 , 4 , 6 and 12
100

What is the first multiple of every number?

The number itself

200

What is the product of an even and an odd number — odd or even?

Even 

Ex: 8 x 9 = 72

200

Are all odd numbers prime?

  1. No (for example, 9 and 15 are odd but not prime).
200

Which is the smallest two-digit composite number?

10

200

Which number has only two factors?

Which is the largest factor of 128? 


Prime Numbers 

128

200

Which is greater the 5th multiple of 4 or the 4th multiple of 5?


  1. Both are equal (20).
300

What type of number will 10 less than an odd number be?

Odd Number

Ex: odd number = 79 - 10 = 69 

300

Which of these pairs are both prime: (13, 15), (17, 19), (21, 23)?


17, 19

300

Which number between 15 and 20 is not composite?

17 and 19

300

Write all common factors of 12 and 18.

1, 2, 3, 6.

300

Which number is a common multiple of 2, 3, and 5?

30

400

The sum of two numbers is 37, and one of them is even. What can you say about the other number?


The other number is odd

Ex: 37 - 8 = 25

400

What is the difference between the largest and smallest prime numbers less than 20?


19 - 2 = 17

400

Write three consecutive composite numbers.


8, 9, 10 (or 14, 15, 16).

400
  1. What is the greatest factor common to 20 and 28?

Factors of 20 = 1 , 2 , 4  ,5 ,10 , 20

Factors of 28 = 1 , 2 , 4 , 7 , 14 , 28

= 4

400

What is the smallest multiple of both 8 and 12?

24

500

Write a 4-digit odd number using digits 2, 5, 8, and 9 without repetition.


  1. 9582 (invalid, ends in even) 
  2. → Correct answer: 9825, 8529, etc. (any ending in an odd digit).
500

If you multiply two prime numbers and add 1, can the result be a prime? Give an example.


  1. Sometimes yes (e.g., 2×3 + 1 = 7, which is prime).
500

Find two composite numbers whose sum is 20.


8 + 12, or 9 + 11 (No—11 is prime!) So correct: 6 + 14 = 20.

500

A number has exactly four factors: 1, 2, 3, and 6. What is the number?

6

500

A number is a multiple of both 9 and 12. What is the smallest such number?

36