HCF of 20 and 21

The HCF of 20 and 21 is 1. The listing common factors, prime factorisation, and long division are the three most frequent methods for calculating the HCF of 20 and 21. The highest number that divides 20 and 21 perfectly, leaving no remainder, is known as the HCF of 20 and 21. The components of 20 and 21 are, respectively, (1, 2, 4, 5, 10, 20) and (1, 3, 7).

Also read: Highest common factor

What is the HCF of 20 and 21?

The answer to this question is 1. This article shows the HCF of 20 and 21 using various methods for your reference. The greatest of all their common factors is the Highest Common Factor (HCF) of two or more numbers.

How to Find HCF of 20 and 21?

There are three methods to find the HCF of 20 and 21:

• Prime Factorisation
• Long Division method
• Listing common factors

HCF of 20 and 21 by Prime Factorisation Method

The prime factorisation of 20 and 21 is given by:

Prime factorisation of 20 = (2 × 2 × 5)

Prime factorisation of 21 = (3 × 7)

Hence, the HCF of 20 and 21 is 1.

HCF (20, 21) = 1

HCF of 20 and 21 by Long Division Method

The divisor that we receive when the remainder becomes 0 after executing long division repeatedly is HCF of 20 and 21.

No further division can be done.

Hence, HCF (20, 21) = 1

HCF of 20 and 21 by Listing the Factors

To calculate the HCF of 20 and 21 by listing out the common factors, list the factors as shown below:

Factors of 20 = 1, 2, 4, 5, 10, 20

Factors of 21 = 1, 3, 7, 21

Therefore, the HCF of 20 and 21 is 1.

Related Articles

• HCF
• HCF of Two Numbers
• HCF and LCM
• Relation between HCF and LCM
• GCF calculator

Video Lesson on Properties of HCF and LCM

HCF of 20 and 21 Solved Example

The product of two numbers is 420. If their HCF is 1, what is their LCM?

Solution:

Given: HCF = 1 and product of numbers = 420

LCM × HCF = product of numbers

⇒ LCM = Product/HCF = 420/1

Therefore, the LCM is 420.