Question

Is 87 a prime number?

Answer 1

`87` is not a prime number but is a composite number.

Explanation:

To check whether a number is a prime number or not, one may take a number less than approximately its square root.

Here a number less than approximately the square root of `87` is `9`, so one needs to try division of `87` by prime numbers up to number `9`.

As prime numbers up to `9` are only `{2,3,5,7}` and number is divisible by `3` (one can check by using divisibility rule),

`87` is not a prime number but is a composite number.

In fact `87=3xx29`