Why Do Prime Numbers Exist?
Some whole numbers cannot be broken into smaller multiplication facts. For example, 7 can only be made with 1 × 7. That makes 7 prime.
Number & operations reference
Prime Numbers
A prime number is a whole number bigger than 1 that can be divided evenly in only two ways: by 1 and by itself. Divided evenly means the answer is a whole number with nothing left over.
Prime example7 ÷ 1 = 7 and 7 ÷ 7 = 1
Not prime12 also divides evenly by 2, 3, 4, and 6
Prime chart
Prime Numbers Through 200
2 is the only even prime number.
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
101
103
107
109
113
127
131
137
139
149
151
157
163
167
173
179
181
191
193
197
199
What Is a Factor?
A factor is a whole number that divides evenly into another whole number. For example, 3 is a factor of 12 because 12 ÷ 3 = 4.
What Does Composite Mean?
A whole number bigger than 1 that is not prime is called composite. It can be divided evenly by more than two whole numbers.
Why should I care?
Prime Numbers Are Building Blocks
Every whole number bigger than 1 is either prime or can be made by multiplying prime numbers together.
Break Apart Numbers
Prime numbers help us break large numbers into smaller multiplication facts.
Solve Other Math
They help with simplifying fractions and finding the GCF and LCM.
Protect Information
Very large prime numbers help protect information sent online.
Remember
The number 1 is not prime because it can be divided evenly in only one way. Also, not every odd number is prime: 9 divides evenly by 1, 3, and 9.
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