No brainer if you are in school but out of school and if some one asks you this question, can you answer it?

Finding factors:{If you are preparing for GMAT this should give you a quick review of what factors are?}

One easy way is through prime numbers as they make it easy to find the factors of a number.

What is a prime number : A number is prime if it cannot be divided evenly by anything except itself and 1. For example, 5 is a

prime number, because the only factors of 5 are

1 * 5 = 5

Let’s consider a number like 121:

how many factors does 121 have?

121 = 11 X 11, 11 is prime number

So prime factors of 121 are 1, 11 and 121

Let’s consider a number like 72 that you want to find factors of It’s even, so it’s divisible by 2:

72 = 2 * 36

Now, what about 36? That’s also even, so it’s divisible by 2:

72 = 2 * 2 * 18

What about 18? That’s divisible by 2:

72 = 2 * 2 * 2 * 9

What about 9? That’s not divisible by 2, but it is divisible by 3:

72 = 2 * 2 * 2 * 3 * 3

And 3 is prime. So what we’ve done here is find the ‘prime factors’ of

the number 72.

How does this help us find all the factors of 72? Well, if a number

is a factor of 72, and it’s not one of these prime factors, then it

must be a product of two or more prime factors. So we can find all the

factors of 72 by looking at all the ways we can group these prime

factors:

2 * 2 = 4 pairs

2 * 3 = 6

3 * 3 = 9

2 * 2 * 2 = 8

2 * 2 * 3 = 12 triplets

2 * 3 * 3 = 18

2 * 2 * 2 * 3 = 24 product of four prime factors

2 * 2* 3 * 3 = 36

So the factors of 72 are

1 A factor of everything.

2, 3 The distinct prime factors.

4, 6,9 Products of two prime factors.

8,12,18 Products of three prime factors.

24,36 Products of three prime factors.

72 Product of all the prime factors.

Now

1,2,3,4,6,8,9,12,18,24,36,72

Factors vs Multiples basics

Factors

Finite number of factors for any whole number

Most factors are smaller than number – largest is number itself

Multiples

Infinite number of multiples

Most multiples larger than number, smallest is number itself

Here are some online links you can use some of the Math formulas

Finding prime factors online

Online Math calculators – A very good resource for all math calculations online.