Answer: (2) 1593

Solution: 2N has 2f means N is not divisible by 2. 

and 6N has 3f factors means factor has become 1.5 times that is 3/2 times. It means when multiplied by 3 factor become 2f to 3f. Hence power of 3 became 1 to 2. Hence N is divisible by 3. 

Only option that is divisible by 3 and not by 2 is option(2).