Any natural number that is not prime can be factorized as a product of prime numbers. This process is known as breaking down numbers into prime factors.

From time to time, to solve a certain exercise in a simpler way, we will have to dfactorize the numbers we are given, and rewrite them as products of prime numbers. This factorization gives the possibility to use the numbers in a more comfortable way, for example, by taking advantage of the properties of powers or exponent laws.

For example: The number $8$ can be written as $2^3$ The number $1176$ can be also written as $2^2\times3\times7^2$

Let's write the number we want to factorize and draw a line next to it. We will ask ourselves what is the smallest prime number by which we can divide without having a remainder (zero remainder).

We will always start with $2$, if the number is not a multiple of $2$ we will go to the next prime number which is $3$, and so on. We will recurse that the first prime numbers are $2, 3 ,5, 7, 11, 13, 17, 19,$ etc. If the number can be divided without remainder we will write the prime number in front of our original number and, below our number, we will write down the quotient (result of the division).

We will continue factoring until we get to the number $1$ in the left column, this number can no longer be broken down. The number we wanted to factorize is equal to the product of all the numbers we wrote down in the right hand column.

For example

Let us factorize the number $64$ as prime factors

Let's ask: Can $64$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $32$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $16$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $8$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $4$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $2$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. We arrive at $1$. We have finished decomposing. Now let's multiply all the factors we wrote down in the column on the right side, we will get: $64=2\times2\times2\times2\times2\times2=2^6$

Now let's look at a more advanced example of factoring natural numbers as a product of powers within an exercise:

$\frac{6^{76}\times8^{-2}}{16^{12}\times9^{28}}=$

Don't be scared of the high exponents or that there is no equality of base.

That is exactly why we have learned to factor, that is, to decompose any natural number as a product of powers.

Let's go term by term and factor as we have learned.

After each factorization we will write down the exercise again so we don't get confused.

Let's start with:

Let's ask: Can $5$ be divided, leaving no remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $3$ be divided, without remainder, by $2$, the smallest prime number? The answer is no. Let us ask: Can $3$ be divided, without remainder, by the next prime number, i.e. $3$? The answer is yes. Let us add to our illustration the $3$ and also the result.

We arrive at the number $1$, we have finished factoring. Now let's multiply all the factors that we wrote down in the column on the right side and we will get:

$6=2\times3$

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Test your knowledge

Question 1

Write all the factors of the following number: \( 7 \)

Let's ask: Can $8$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $4$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $2$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. We arrive at $1$, we have finished decomposing. Now let's multiply all the factors we wrote down in the column on the right side and we will get:

Let's ask: Can $16$ be divided, without leaving remainder, by $2$, the smallest prime number? The answer is yes.

Let's add to our illustration the $2$ and also the result.

Let's ask: Can $8$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $4$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. Let's ask: Can $2$ be divided, without remainder, by $2$, the smallest prime number? The answer is yes. Let's add to our illustration the $2$ and also the result. We arrive at $1$. We have finished decomposing. Now let's multiply all the factors we wrote down in the column on the right side and we will get:

Let's continue with the factorization of the. $9$:

Let's ask: Can the $9$ be divided, without leaving remainder, by $2$, the smallest prime number? The answer is no. Let's continue with the prime number that comes after $2$ Let's ask: Can $9$ be divided, without remainder, by the next prime number, that is $3$? The answer is yes. Let's add to our illustration the $3$ and also the result.

Let's ask: Can $3$ be divided, without remainder, by $2$, the smallest prime number? The answer is no. Let's continue with the prime number that comes after $2$ Let's ask: Can $3$ be divided, without remainder, by the next prime number, that is $3$? The answer is yes. Let's add to our illustration the $3$ and also the result. Now let's multiply all the factors that we wrote down in the column on the right side and we will get:

Well, now we can apply in the denominator the law of the product of powers with equal bases and add the exponents of base $2$.

We will obtain:

$\frac{2^{76}\times3^{76}}{2^{54}\times3^{56}}=$

Great! Our next step will be, no doubt, to use the quotient property of powers with equal base: Subtract the exponent of the numerator minus the exponent of the numerator where there is equality of bases.

This step will relieve us of the nuisance of the fraction and we will be left with a much simpler expression with reduced exponents:

We will do this and obtain:

$2^{22}\times3^{20}$

Notice how factorizing numbers into prime factors in conjunction with the properties of exponents help to solve exercises in a very simple way.

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What does it mean to break down a number into factors?

It is when we represent a number as a product of others. For example:

$24=2\times12$

$24=3\times8$

$24=4\times6$

$24=2\times2\times2\times3$

How do we factorize?

To factorize we must make successive divisions until the quotient is one. For this we place our number and on the right side a vertical bar, we look for a divisor and place it on the right side, the quotient on the left side and repeat the process now looking for a divisor of the previously obtained quotient, until we get a one on the left side. Our initial number can be written as the product of all the divisors placed on the right side of the vertical line.

How we do prime factorization?

To break a number down into prime factors, we place the number and a vertical line to its right. We look for the smallest prime divisor of our number and we place it on the right side of the vertical line, the quotient we write it on the left side, just below the number we want to decompose. We repeat the process now looking for the smallest prime divisor of the quotient obtained previously and we continue this way until we obtain a quotient $1$.

Test your knowledge

Question 1

Write all the factors of the following number: \( 99 \)