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Is 81 a Prime Number?

Is 81 a prime number? Numbers having only 2 factors, i.e. 1 and the number itself are known as prime numbers whereas numbers with more than 2 factors are known as composite. The answer to the question whether 81 is a prime or composite is - "81 is a composite number." Now, let us find out how and why is 81 a prime number or a composite number?

Is 81 a prime number? - No
Is 81 a composite number? - Yes
Is 81 a perfect square? - Yes
Prime Factors of 81 - 3
Factors of 81 - 1, 3, 9, 27, 81

Is 81 a Prime or Composite?

Is 81 a Prime Number?

No, 81 is not a prime number. The number 81 is divisible by 1, 3, 9, 27, 81. For a number to be classified as a prime number, it should have exactly two factors. Since 81 has more than two factors, i.e. 1, 3, 9, 27, 81, it is not a prime number.

Is 81 a Prime Number?

Why is 81 not a Prime Number?

To understand whether 81 is composite or prime, it is important to find its factors.

Factors of 81: 1, 3, 9, 27, 81

Since 81 has more than 2 factors, we can say that 81 is not a prime number.

☛ Prime Number Calculator

Is 81 a Composite Number?

Yes, since 81 has more than two factors i.e. 1, 3, 9, 27, 81. In other words, 81 is a composite number because 81 has more than 2 factors.

Problem Statements:

Is 81 a Prime Number?	No
Is 81 a Composite Number?	Yes
Cube Root of 81	4.326742
Multiples of 81	81, 162, 243, 324, 405, 486, 567, 648, 729, 810
Square Root of 81	9
Square of 81	6561
Is 81 a Perfect Square?	Yes
Is 81 an Even Number?	No
Is 81 an Odd Number?	Yes
Is 81 a Perfect Cube?	No

Fun Facts:

All primes except 2 are odd.
Prime numbers greater than 5 can be represented in the form of either 6n + 1 or 6n - 1. Example - 71 is a prime number and it can be written as 71 = 6 × 12 - 1
Euler discovered a polynomial n² + n + 41 that produces prime numbers for values of n that lie between 0 and 39 inclusive. It can generate 40 prime numbers for 0 <= n <= 39.

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