Factors of a Number: In mathematics, a factor is a number that divides another number perfectly, leaving no remainder. Factors can also be seen as pairs of numbers that, when multiplied together, result in the original number. For example, 2 and 3 are factors of 6 because multiplying them together gives 6. A single number can have multiple factors.
Let’s learn about the factors of prime and composite numbers, common factors, and methods to find them.
What are Factors?
Factors of a number can be defined as the divisors which divide the number exactly without leaving any number. Every number other than 1 has at least two factors, 1 and the number itself.
For example:
- Factors of 4 are 1, 2, and 4 as when we divide 1,2 and 4 by 4, it will evenly divide it by leaving 0 as the remainder.
- Factors of 24 are 1, 2, 3, 4, 6, 8, 12 and 24. As 24 is exactly divisible by all these numbers.
Factors of a Number Definition
In mathematics, factors of a number are defined as whole numbers that can be multiplied together to produce the original number. In other words, a factor of a number divides that number without leaving any remainder.
Factors of a Number Properties
These are some of the key properties of the factors of a number:
- Zero cannot be a factor of any number as division by 0 is not defined.
- 1 is a factor of every number.
- Every number has at least 2 factors, 1 and the number itself
- A factor can be negative.
- A factor of a number is always smaller than or equal to the number.
- 1 is the smallest factor of a number and the number itself is the greatest factor of the number.
- A factor of a number can never be a decimal or a fraction.
- 2 is a factor of every even number.
- 5 is a factor of every number that has 5 or 0 in its unit place.
How to Find Factors of a Number?
We can find all the factors of a given number in the following two ways:
- Multiplication method
- Division Method
- Factor Tree Method
Finding Factors Using Multiplication Method
In this method, we have to find all the pairs of whole numbers whose product is equal to the given number. Let us consider an example to understand that better.
Example: Find all the factors of 12 using the multiplication method.
Solution:
We have to find all the pairs of whole numbers whose product is 12, like
1 × 12 = 12
2 × 6 = 12
3 × 4 = 12
Here the product of the following pairs is 12.
(1, 12) , (2, 6) and (3, 4)
Hence, all these numbers 1, 2, 3, 4, and 12 are factors of 12.
Finding Factors Using Division Method
In this method, we have to find all the divisors of the given number which are exactly divisible by it. Here we start dividing the given number by 1 and continue dividing it by the next number until we reach the square root of that number (or until we reach the number itself).
If the number exactly divides the original number then it is a factor else not. Let us consider an example to understand that better.
Example: Find all the factors of 12 using the division method.
Solution:
We will take every natural number less than 12 and will check whether it is divisible by 12 or not
- 12 ÷ 1 = 12 (remainder = 0)
- 12 ÷ 2 = 6 (remainder = 0)
- 12 ÷ 3 = 4 (remainder = 0)
- 12 ÷ 4 = 3 (remainder = 0)
- 12 ÷ 5 = 2 (remainder = 2)
- 12 ÷ 6 = 2 (remainder = 0)
- 12 ÷ 7 = 1 (remainder = 5)
- 12 ÷ 8 = 1 (remainder = 4)
- 12 ÷ 9 = 1 (remainder = 3)
- 12 ÷ 10 = 1 (remainder = 2)
- 12 ÷ 11 = 1 (remainder = 1)
- 12 ÷ 12 = 1(remainder = 0)
So, the numbers that are exactly divides 12 are 1, 2, 3, 4, 6, and 12. Hence these numbers are the factors of 12.
Prime Factorization by Factor Tree Method
A factor tree is a diagrammatic representation of the prime factors of a number. In this method, we find the factors of a number and then further factorize them until we get all the factors as prime numbers. Here, we consider the given number as the top of a tree and all its factors as its branches.
To find the prime factorization by factor tree method, we follow the below given steps:
- First, split the given number (which is placed at the top of the tree) into factors.
- Then write down the factor pair as the branches of the tree.
- Again split the composite factors obtained in step 2.
- Repeat steps 2 and 3 until all the factors become prime numbers.
- Lastly, multiply all the prime factors obtained.
How To Check whether a Number is a Factor
To check whether the given number (first number) is a factor of another number (second number) or not we divide the numbers, if the remainder is 0 then it is a factor else not.
Example 1: Check if 21 is a factor of 525 or not.
Solution:
We will check the divisibility of 525 with 21
On evaluating we get, 525 ÷ 21 = 25, with remainder 0
Here 525 is exactly divisible by 21. Hence 21 is a factor of 525.
Factors of Prime Numbers
Prime Numbers are the numbers that have exactly and only two factors, i.e. 1 and the number itself. For example: 2, 3, 19, 89, etc are prime numbers. To find all the factors of a prime number simply write 1 and the prime number itself.
- 2 is the only even prime number.
- The smallest prime number is 2.
- The smallest odd prime number is 3.
Read More: Prime Numbers
Factors of Composite Numbers
Composite Numbers are those that have more than two factors. For example: 4, 9, 25, 105, etc are composite numbers. All the other natural numbers (except 1) which are not prime are composite. 4 is the smallest composite number.
We can find all the factors of the composite number by using multiplication or division method.
Note: 1 has only one factor so it is neither prime nor composite.
Read More: Composite Numbers
Factors of Square Numbers
A square number can be defined as a product of some integer with itself. For example, 9 is a square number which is obtained by multiplying 3 by 3. Similarly, 16 is the square number obtained by multiplying 4 by 4. Factors of a square number can be obtained by using any method of factorization be it division method or multiplication method. For example,
- Factors of 16 are 1, 2, 4, 8, and 16.
- Similarly, factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, and 36.
- A square number is always positive.
- The unit digit of a Square number can never be 2, 3, 7, or 8.
- The factors of square numbers 0 and 1 are 0 and 1 respectively.
Common Factors
The common factors are those factors that are common (same) to two or more numbers. These are the factors that divide each of them evenly.
Example: Find common factors of 10 and 15.
Solution:
Factors of 10 are: 1, 2, 5, 10
Factors of 15 are: 1, 3, 5, 15
We can see 1 and 5 are common in both 10 and 15. Hence 1 and 5 are common factors of 10 and 15.
Prime Factors of a Number
The prime numbers whose product gives back the original number are said to be the prime factors of that number. Prime factors can not be further divided.
For example 2 × 2 × 5 = 20, Hence the prime factors of 20 are 2, 2, and 5.
Read More : Prime Factorization
We can easily write any natural number as a product of its prime by using the prime factorization method discussed above.
Let us suppose N is a natural number with prime factors Xp × Yq × Zr, where
- X, Y, Z are prime numbers and
- p, q, r are their respective powers.
The basic factor formulas are:
- Sum of Factors
- Number of Factors
- Product of Factors
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Formulas to Find the Factors
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Name
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Formula
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Sum of Factors
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[(X p+1-1)/X-1] × [(Y q+1-1)/Y-1] × [(Z r+1-1)/Z-1]
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Numbers of Factors
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(p+1) (q+1) (r+1)
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Product of Factors
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NTotal No. of Factors/2
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Sum of Factors
The sum of factors refers to finding the sum of all the factors of a number. The formula to find the sum of all factors of a number N is:
Sum of factors of N = [(X p+1-1)/X-1] × [(Y q+1-1)/Y-1] × [(Z r+1-1)/Z-1]
Number of Factors
A number of factors simply means a total number of factors of a number. We can easily find the number of factors by the formula:
Number of Factors for N = (p+1) (q+1) (r+1).
Product of Factors
The product of factors refers to the product of all the factors of a number. The formula to calculate the product of factors is:
Product of factors of N = NTotal No. of Factors/2
Factors and Multiples
Factors and Multiples are studied simultaneously in mathematics. Factors are the numbers which divides a number while multiples are the numbers which are obtained by multiplying a number with other number.
Difference between Factors and Multiples
Let’s compare Factors and Multiples in the table below :
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Factors vs. Multiples
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Factors
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Multiples
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| Factors are the divisors of a number that divides the number without leaving any remainder |
Multiples are the product obtained by multiplying the number with other number |
| Every Number is a Factor of itself |
Every Number is a Multiple of itself |
| A number is the largest factor of itself |
A number is the smallest multiple of itself |
| Number of Factors of a Number is finite |
Number of Multiples of a Number is infinite |
| Factor of a number is smaller or equal to the number |
Multiple is equal or larger than the given number |
| Factor is found by dividing the number |
Multiple is found by multiplication |
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Solved Examples on Factors of Numbers
Example 1: Find all the factors of 64 by multiplication method.
Solution:
Factors of 64
- 1 × 64 = 64
- 2 × 32 = 64
- 4 × 16 = 64
- 8 × 8 = 64
Hence the factors of 64 are 1, 2, 4, 8, 16, 32, and 64.
Example 2: Find common factors of 24 and 48.
Solution:
Factors of 24 = 1, 2, 3, 4, 6, 8, 12, and 24
Factors of 48 = 1, 2, 3, 4, 6, 8, 12, 16, 24, and 48
Hence the common factors of 24 and 48 are 1, 2, 3, 4, 6, 8, 12, and 24.
Example 3: Find all the factors of 32 by division method.
Solution:
Factors of 32
- 32 ÷ 1 = 32
- 32 ÷ 2 = 16
- 32 ÷ 4 = 8
Hence the factors of 32 are 1, 2, 4, 8, 16, and 32.
Example 4: Check if 50 is a factor of 1550 or not.
Solution:
We have to check the divisibility of 50 and 1550
1550 ÷ 50 = 31 ( with remainder 0)
Hence 1550 is exactly divisible by 50 so 50 is a factor of 1550.
Practice Questions on Factors of Number
Q1: Find all factors of 28 and 36.
Q2: Check if 12 is a factor of 144 or not.
Q3: Find prime factorization of 169.
Q4: Find prime factorization of 640.
Q5: Find common factors of 12, 24 and 48.
FAQs on Factors of a Number
Define Factors.
Factors are the numbers that exactly divide the given number i.e. always leaving 0 as a remainder. A factor can never be negative, a fraction or a decimal, It is always a whole number.
What are the Factors of 0 and 1?
0 is a universal dividend that has infinite factors but the only factor of 1 is 1 itself.
How to determine whether a Number is Prime or not?
If a number has only two factors i.e. 1 and the number itself then that number is said to be prime.
What is the Difference between Factors and Multiples?
Factors are the numbers that exactly divide the given number whereas Multiples are obtained by multiplying the given number with another number. For example:
- Factors of 6 are 1, 2, 3, and 6
- Multiples of 6 are 6, 12, 18, 24 and so on.
What are Prime Factors of a Number?
The prime numbers whose product gives back the original number are said to be the prime factors of that number. For example prime factors of 12 = 2 × 2 × 3 = 22 × 3.
What are the Factors of 100?
Factors of 100 are:
- 1 × 100 = 100
- 2 × 50 = 100
- 4 × 25 = 100
- 5 × 20 = 100
- 10 × 10 = 100
Hence factors of 100 are 1, 2, 4, 5, 10, 20, 25, 50, and 100.
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