Asked by Anonymous

Is 89 prime or composite
Answered by oobleck
does 2 divide 89? No
Does 3? No
Does 5? No
Does 7? No
We're done, since we have checked all the primes less than √89.
If it has any other larger prime factors, then it will also have a factor less than √89, but we have shown this not to happen.
So 9 is prime.