Prime and Prime and Composite Composite NumbersNumbers

Prime and Composite Prime and Composite NumbersNumbers

Divisibility RulesDivisibility RulesA number is divisible by…A number is divisible by… DivisibleDivisible Not Not

DivisibleDivisible

22 If the last digit is even If the last digit is even (0,2,4,6,8)(0,2,4,6,8)

3,973,9788 4,974,9755

33 If the sum of the digits is If the sum of the digits is divisible by 3divisible by 3

315315 139139

44 If the last two digits form a If the last two digits form a number divisible by 4number divisible by 4

8,58,51212 7,57,51818

55 If the last digit is 0 or 5 If the last digit is 0 or 5 14, 9714, 9755 10, 10, 979788

66 If the number is divisible by If the number is divisible by both 2 and 3both 2 and 3

4848 2020

99 If the sum of the digits is If the sum of the digits is divisible by 9divisible by 9

711711 9393

1010 If the last digits is 0If the last digits is 0 15,9915,9900 10,5310,5366

Prime and Composite Prime and Composite NumbersNumbers

Definitions Definitions Prime Number ~ is divisible by only Prime Number ~ is divisible by only

the numbers 1 and itself. the numbers 1 and itself. Composite Numbers ~ Numbers that Composite Numbers ~ Numbers that

are divisible by more than two are divisible by more than two numbers.numbers.

Divisible ~ Can be divided by a Divisible ~ Can be divided by a number without leaving a remainder. number without leaving a remainder. (factors)(factors)

Prime Numbers 1-50Prime Numbers 1-50

11 22 33 44 55 66 77 88 99 1010

1111

1212 1133

1414 1515 1616 1177

1818 1199

2020

2121 2222 2233

2424 2525 2626 2727 2828 2299

3030

3311

3232 3333 3434 3535 3636 3377

3838 3939 4040

4411

4242 4433

4444 4545 4646 4477

4848 4949 5050

Example AExample A

Prime or Composite?Prime or Composite?

4545

Divisible by: 1, 3, 5, 9, 15, 45Divisible by: 1, 3, 5, 9, 15, 45

CompositeComposite

Example BExample B

Prime or Composite?Prime or Composite?

1313

Divisible by: _______________Divisible by: _______________

Answer? Answer?

Example CExample C

Prime or Composite?Prime or Composite?

4949

Divisible by: _________________Divisible by: _________________

Answer?Answer?

Example DExample D

Prime or Composite?Prime or Composite?

1919

Divisible By: __________________Divisible By: __________________