Cleanest way to check if a number is an integer.

[Candystore]

So I need to find factors of my numbers to speed up my algorithm and I'm dividing by prime factors and to find them I obviously need to know if they are still integers after I divide into each prime. For 2 and 3 this is easy, since I can do simple bit operations before I divide. For any prime | prime > 3, I want to do a brute force approach and check if my result is an integer or a fraction.

I thought about this and I could use %, if % > 0, I have a fraction.

I could put the result in an integer and in a float, if float and integer differ, I have a fraction.

I could simply use a float, do a bit operation on the exponent part (bits 2-9 iirc) to see if the float has a decimal.

I could use Math.Truncate(double) from the .Net library which takes out the integer part for me, if I check thsi against the double and if it's not 0, I have a fraction.

Which method would you use?