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Is 21 a Prime Number?

Is 21 a prime number? "No, 21 is not a prime number." A number can be classified as prime or composite depending on the factors it contains; it could either have only 2 factors or more than 2 factors. Numbers like 631 with only 2 factors, i.e. 1 and 631 are called prime numbers. However, numbers like 340 with more than 2 factors are called composite numbers. Let us find out how and why is 21 a prime number or a composite number?

Is 21 a prime number? - No
Is 21 a composite number? - Yes
Prime Factors of 21 - 3, 7
Is 21 a perfect square? - No
Factors of 21 - 1, 3, 7, 21

Is 21 a Prime or Composite?

Is 21 a Prime Number?

No, 21 is not a prime number. The number 21 is divisible by 1, 3, 7, 21. For a number to be classified as a prime number, it should have exactly two factors. Since 21 has more than two factors, i.e. 1, 3, 7, 21, it is not a prime number.

Is 21 a Prime Number?

Why is 21 not a Prime Number?

To understand whether 21 is prime or composite, it is important to find its factors.

Factors of 21: 1, 3, 7, 21

Since 21 has more than 2 factors, we can say that 21 is not a prime number.

☛ Prime Number Calculator

Is 21 a Composite Number?

Yes, since 21 has more than two factors i.e. 1, 3, 7, 21. In other words, 21 is a composite number because 21 has more than 2 factors.

Problem Statements:

Is 21 a Prime Number?	No
Is 21 a Composite Number?	Yes
Is 21 a Perfect Square?	No
Is 21 an Odd Number?	Yes
Multiples of 21	21, 42, 63, 84, 105, 126, 147, 168, 189, 210
Cube Root of 21	2.758921
Is 21 an Even Number?	No
Is 21 a Perfect Cube?	No
Square Root of 21	4.582576
Square of 21	441

Fun Facts:

Numbers X and Y are said to be coprime if they have only one common factor that is 1.
All primes except 2 are odd.
23 is the smallest prime number having consecutive digits.

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