Is 81 a prime number?

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Is 81 a prime number?

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Answer 1 · 2016-04-03T02:45:47

$81$ $81$ is not prime but composite.

Explanation:

A number is prime if it would S not divisible by any number other than $1$ $1$ and itself. To check one needs to try to divide the number at least up to a prime number, which is just less than its square root.

$81$ $81$ has an exact square root in $9$ $9$ and hence divisible by $9$ $9$ as also $3$ $3$ and $27$ $27$ . It is in fact fourth power of $3$ $3$ that is $81 = 3 \times 3 \times 3 \times 3 = 3^{4}$ $81=3xx3xx3xx3=3^4$ .

Hence $81$ $81$ is not prime but composite.

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Is 81 a prime number?

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