Question

Is $ 81 $ a prime number?

Answer 1

Hint: A prime number can be well-defined as the positive integer which is having exactly two factors. If “n” is the prime number then it has only two factors that is the number itself “n” and the number here, we will find the factors for all the numbers and then will find out whether it is prime or not based on the number of factors it has.

Complete step-by-step answer:
Given number: $ 81 $
The factors of the given number can be found by using the prime factorization method, long division method or the factor tree method.
 $
  81 = 9 \times 9 \\
  81 = 3 \times 3 \times 3 \times 3 \;
 $
Since, the given number is having more than two factors, it is not the prime number and hence the given number is a composite number.

Note: Always remember that the number $ 1 $ is neither prime nor composite number. Be good in multiples and division to get the prime number. Know the difference between the prime numbers and the composite numbers and apply it accordingly.