Prime
and Composite Numbers
prime
composite
composite
Prime Numbers
What is a prime number?
A prime number is a whole number that has exactly two factors: 1 and the
number itself.
2
Example:
2 1 x 2
1
x
The factors of 2 are 1 and 2.
This makes 2 a prime number.
2
Why is 12 not a prime number?
12
1 x 12
2 x 6
3 x 4
12
6
3
x
x 2
The number 12 is not a prime number because it has
more factors then 1 and itself.
2
What is a composite number?
A composite number is a number that can be broken down into two or more
factors.
Example: factors of 16 = 1, 2, 4, 8, 16.
16 is a composite number.
What are composite numbers between 1 and 30?
Compute the prime
factorization using stair
steps.
First, make a small list of prime numbers for reference..
Second, build the steps by dividing
into 16 using only prime numbers as
divisors.
Third, write the equation.
Prime Factorization
16
2 x 2 x 2 x 2 = 24
Compute the prime
factorization using stair
steps.
First, make a small list of prime numbers for reference..
Second, build the steps by dividing
into 50 using only prime numbers as
divisors.
Third, write the equation.
Prime Factorization
50
2 x 5 x 5 = 2 x 52
Compute the prime
factorization using stair
steps.
First, make a small list of prime numbers for reference..
Second, build the steps by dividing
into 315 using only prime numbers as
divisors.
Third, write the equation.
Prime Factorization
78
2X3X13
Use the division method to find the prime factorization.
27
60
100
1
Which of the following
Multiple answer
numbers are prime numbers?
A
51
B
7
C
29
D 9
Which of the following
numbers are composite
numbers?
2
A
8
B
23
C
36
D
41
Multiple answer
Which of the following
numbers are prime factors
of 45?
3
A
2, 2, 7
B
3, 3, 5
C
3, 3, 7
D
5, 5, 7
Multiple choice
4
How many prime numbers
are there between 1 and
25?
A 9
B 12
C 14
D 15
Multiple choice
Fill in the blanks with the correct word.
1. A _________________________ number has exactly 2 factors, ______________ and itself.
2. A composite _________________________ has ______________ than two factors.
3. A factor is a number that _______________________ into
a whole number _______________ leaving a remainder.
3
19
77
31
Prime Numbers
Storage Box
11
99
12
54
100
17
2