Prime Prime Prime Help Help Help

hi everyone, i have being working on this code for a long time.. but couldnt make it right

it is simple find the prime number from the user inputs

this is the code ....

Code:

`bool IsPrime(int iNum)`

{

// Check if i is less than square root of iNum (and cast iNum to type double)

for (int i=2; i<=sqrt((double)iNum); i++)

{

if (iNum == ((int)iNum/i)*i)// (inum%i == 0)

return false;

}

return true;

}

but this is not the exact code that i want ...

my aim is to find the prime number that the user will input the max number,,,

example here:

input: 4

output will be: not prime..

please help ...... i know there are lot of related topic but .... still couldnt help.