Composite Number:
A positive integer which can be divided by at least one more number except one and itself is said to be composite number.
Example: 4 is composite no. as it has a factor ‘2’ which is different from 1 and 4 itself.
Facts:
- Every positive integer greater than 1 is either composite or prime.
- Composite no. can’t be a prime number.
- 1 is neither composite nor prime number.
- We can write every composite number as the product of two or more primes.
Smallest Composite Number:
4 is the smallest composite number in the number system.
We can explain it as
- 1 is neither a prime nor a composite.
- 2 is a prime number.
- 3 is also a prime number as 1 and 3 itself is the only factor.
- If we talk of 4. It has 1, 2 and 4 as its factors. It has 2 as a factor except 1 and 4 itself and can’t be considered as prime so 4 is the smallest composite number.
Composite Number list:
The list of composite numbers up to 100 is provided below. Take a look into it.
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.
By this composite numbers chart, you can differentiate between prime numbers and composite numbers easily.
Is 2 a composite number?
No, 2 is not a composite number.
We can explain it as we know, according to the definition of composite numbers there should be at least one factor other than the number itself. But in the case of 2, we see that there is no any factor other than 1 and 2 itself is present so it is a prime number, not a composite no.
Is 21 a composite number?
Yes, 21 is a composite number.
Following the definition of composite no. if we notice 21 we see that it has factors 1, 3, 7, 21 which satisfies that it has more factors than 1, and 21 itself i.e. 3 and 7.
There is a simple rule to say about the composite numbers. When we have to check whether the number is prime or composite we simply use to factor it out by least prime numbers up to 10. we easily get the result in general cases.