### What are composite numbers ?

Any number other than 1, which is not a prime number is a composite number.Thus a composite number is a number which has at least one factor other than 1 and itself.

Every composite number can be written as the product of 2 or more distinct prime numbers.

The number 1 is neither prime nor composite.

### Classification based on number of distinct prime factors:

- 4 = 2 x 2 6=2 x 3

**semiprime**. One of the factors can even be a square of a prime number.

12 = 2 x 2 x 3

12 is multiple of 2 distinct primes 2 and 3. Thus 12 is also a semi prime number.

- 30 = 2 x 3 x 5

Those composite numbers which have 3 distinct prime factors is called a

**sphenic number.**

### Classification based on repetition of prime factors:

Composite number |

- 64 = 2
^{6}

**powerful**number. Thus 64 is a powerful number.

- 210 = 7 x 5 x 2 x 3

When none of the prime factors of a number are repeated, the number is called a

**squarefree**number.

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*Also See :-**What are Perfect Numbers ?*

What is a Co-prime or Relatively prime number ?

Definition of prime number

Properties of Integers