Composite number

Composite number

Hello ScienceBee, in this lesson, we are going to learn about composite numbers. 
 

 

What is a composite number?

A composite number is a positive integer that can be formed by multiplying together two smaller positive integers.
Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. 
Every positive integer is composite, prime, or the unit 1, so the composite numbers are exactly the numbers that are not prime and not a unit.
For example, the integer 14 is a composite number because it is the product of the two smaller integers 2 × 7. Likewise, the integers 2 and 3 are not composite numbers because each of them can only be divided by one and itself.
Video: Prime and Composite numbers

 

List the composite numbers up to 150.

The composite numbers up to 150 are
4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 132, 133, 134, 135, 136, 138, 140, 141, 142, 143, 144, 145, 146, 147, 148, 150. 

 

What is the fundamental theorem of arithmetic?

Every composite number can be written as the product of two or more (not necessarily distinct) primes. For example, the composite number 299 can be written as 13 × 23, and the composite number 360 can be written as 23 × 32 × 5; furthermore, this representation is unique up to the order of the factors. This fact is called the fundamental theorem of arithmetic. 

 

How to recognize composite number and prime numbers?

This video shows how to recognize composite number and prime numbers?

 

Is 1 a composite number?

This video shows if 1 is a composite number.

 

Let's Review

  1. A ____ number is a positive integer that has at least one ____ other than 1 and itself. 
  2. Every composite number can be written as the ____ of two or more (not necessarily distinct) ____ . 

     

    Answer

    1. A composite number is a positive integer that has at least one divisor other than 1 and itself. 
    2. Every composite number can be written as the product of two or more (not necessarily distinct) primes. 

     

    Test Your Knowledge

     

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