What are composite numbers?

Composite numbers are the numbers that are divisible by more than two factors other than 1 and itself. For example;

1. 4, it is divisible by 1,2,4 which means it has more factors other than 1 and 4 (itself) so it is a composite number.
2. 6, it is divisible by 1,2,3,6 i.e. it has more factors other than 1 and 6 so it is also a composite number.

4 is the smallest and the starting composite number and 1 is neither a prime number nor a composite number. When two small positive integers get multiplied then a composite number is formed.

Examples of composite numbers between 1 to 200:

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, 152, 153, 154, 155, 156, 158, 159, 160, 161, 162, 164, 165, 166, 168, 169, 170, 171, 172, 174, 175, 176, 177, 178, 180, 182, 183, 184, 185, 186, 187, 188, 189, 190, 192, 194, 195, 196, 198, 200.

Definition of composite number:

A composite number is a positive integer that is divisible by any positive whole number but other than 1 or itself i.e it should not be a prime number. For example; 8 is divisible by 1,2,4,8 so it is a composite number while 3 is divisible by only 1 and itself 3 so it is not a composite number. These are the natural numbers having more than two factors.

The composite number can also be written as the multiplication of positive prime integers. For example; 325 is a composite number and can be written as 13 × 25 and 24 is also a composite number that can be written as 23 × 31.

Primality test is used to determine that either a number is a prime number (a number which is divided by 1 and itself is known as a prime number for example; 3,5 etc.) or a composite number.

Types of composite numbers

There are two types of composite numbers; odd composite numbers and even composite numbers.

• Odd composite numbers: These are the composite numbers that are odd in nature and also divisible by more than two factors other than 1 and itself like 9,15,21,25 etc. The smallest odd composite number is 9.
• Even composite numbers: These are the composite numbers that are even in nature and also divisible by more than two factors other than 1 and itself like 4,6,8,10,12 etc. The smallest even composite number is 4.

How to find whether the number is composite or not?

Follow the following steps to find the composite numbers;

1. Simply, find the factors of the number by divisibility method you want to identify.
2. Then, if it has more than two factors other than 1 and itself then it is a composite number otherwise not.

Properties of composite numbers:

The properties of composite numbers by which it gets differentiated from other types of numbers are;

1. It can be divided by positive integers other than 1 and itself.
2. A composite number contains a prime number while a prime number does not have a composite number.
3. It has both odd and even numbers even more than the prime number contains.
4. We can write a composite number as the product of two positive integer whole numbers.
5. It has two or more factors.

Conclusion:

The numbers which have more than two factors other than unit 1 and itself are known as composite numbers. We can find the factors by either the highest common factor method (HCF) or the lowest common factor method (LCM). Prime numbers are the ones that have only two factors i.e. divisible only by 1 and itself its number.  We perform a divisibility method to identify whether the number is a prime number or composite number. A composite number is made up of prime numbers. Composite numbers may be regarded as prime numbers but prime numbers cannot be regarded as composite numbers.