# 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 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.

## 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.

## 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 n
^{2}+ 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.

**☛ Also Check: **

- Is 99 a Prime Number? - No
- Is 14 a Prime Number? - No
- Is 75 a Prime Number? - No
- Is 41 a Prime Number? - Yes
- Is 21 a Prime Number? - No
- Is 151 a Prime Number? - Yes
- Is 283 a Prime Number? - Yes
- Is 419 a Prime Number? - Yes

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