##140=2xx2xx5xx7##

To write any number as a product of its prime factors, we should find all those which when multiplied together form the number. Note that in such factorization, **prime numbers can get repeated as well**, but what is important is that

**(1)** all numbers are prime

**(2)** and their product is given number

Hence, we should divide the given number consistently by prime numbers starting with ##2##, which is first prime number and continue till all factors are prime numbers.

Before we try this for given number ##140##, let us list first few prime numbers, which are ##{2,3,5,7,11,13,17,19,23,29,…}##

Now ##140##

= ##2xx70## (and as ##70## can be divided by ##2## again)

= ##2xx2xx35##

= ##2xx2xx5xx7##

As now we have all prime factors, the process is complete and prime factors of ##140## are ##2xx2xx5xx7##.