How to find the prime number: Any even number other than 2 will not be a prime number. If there are 5 at the end of two or more numbers then the number will not be prime. If we want to check whether a number is prime (2 , 3 , 5 , 6 , 11 , 18 , 19) then we can understand. The quotient will not be divisible regardless. Or the sum of 2 , 3 , 5 , 6 should be divided by 18. For example, the number 69 cannot be divided by any of the above. So 69 prime 161 can be divided by 6 so 181 is not a prime number.