In mathematics, the greatest common divisor of two or more integers, which are not all zero, is the largest positive integer that divides each of the integers. In this video, you will learn how to find the HCF in 6th grade math unit. GMAT Number Properties Lesson Video # 9 | Number Properties | GMAT Preparation Online. HCF (Highest Common Factor) or GCD (Greatest Common Divisor) | Don't Memorise. The greatest number which divides each of the two or more numbers is called HCF or Highest Common Factor. HCF : The largest number that divides two or more numbers is the highest common factor (HCF) for those numbers.