OK, please use code tags not output tag on code. (and your output tag failed)
if (1>n>1000) this looks very wrong...
how can n be more than a thousand yet less than 1??
I think what you want is use the OR like this,
if (n < 1 || n > 1000)
cout << "Incorrect Value";
The reason it outputs:
YES YES YES
is probably because n/2 is a non zero value with zero representing false. If you enter bellow 10 but above 1 you probably will get atleast 1 NO.
But seriously what the hell is this program for?
Oh, i get what you want now, there is something called modulus(%).
You use it to get the remainder example:
4%3 = 1 because that is the remainder. If the remainder is 0 you know it can be divided without leftovers. So you would have to change your if statements