LCM of 18 and 21 is the smallest number among all common multiples of 18 and 21. The first few multiples of 18 and 21 are (18, 36, 54, 72, 90, . . . ) and (21, 42, 63, 84, 105, 126, 147, . . . ) respectively. There are 3 commonly used methods to find LCM of 18 and 21 - by division method, by listing multiples, and by prime factorization.

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1. | LCM of 18 and 21 |

2. | List of Methods |

3. | Solved Examples |

4. | FAQs |

**Answer:** LCM of 18 and 21 is 126.

**Explanation: **

The LCM of two non-zero integers, x(18) and y(21), is the smallest positive integer m(126) that is divisible by both x(18) and y(21) without any remainder.

The methods to find the LCM of 18 and 21 are explained below.

By Prime Factorization MethodBy Division MethodBy Listing Multiples### LCM of 18 and 21 by Prime Factorization

Prime factorization of 18 and 21 is (2 × 3 × 3) = 21 × 32 and (3 × 7) = 31 × 71 respectively. LCM of 18 and 21 can be obtained by multiplying prime factors raised to their respective highest power, i.e. 21 × 32 × 71 = 126.Hence, the LCM of 18 and 21 by prime factorization is 126.

### LCM of 18 and 21 by Division Method

To calculate the LCM of 18 and 21 by the division method, we will divide the numbers(18, 21) by their prime factors (preferably common). The product of these divisors gives the LCM of 18 and 21.

**Step 3:**Continue the steps until only 1s are left in the last row.

The LCM of 18 and 21 is the product of all prime numbers on the left, i.e. LCM(18, 21) by division method = 2 × 3 × 3 × 7 = 126.

### LCM of 18 and 21 by Listing Multiples

To calculate the LCM of 18 and 21 by listing out the common multiples, we can follow the given below steps:

**Step 1:**List a few multiples of 18 (18, 36, 54, 72, 90, . . . ) and 21 (21, 42, 63, 84, 105, 126, 147, . . . . )

**Step 2:**The common multiples from the multiples of 18 and 21 are 126, 252, . . .

**Step 3:**The smallest common multiple of 18 and 21 is 126.

∴ The least common multiple of 18 and 21 = 126.

**☛ Also Check:**

## FAQs on LCM of 18 and 21

### What is the LCM of 18 and 21?

### What is the Least Perfect Square Divisible by 18 and 21?

The least number divisible by 18 and 21 = LCM(18, 21)LCM of 18 and 21 = 2 × 3 × 3 × 7

### Which of the following is the LCM of 18 and 21? 21, 3, 28, 126

The value of LCM of 18, 21 is the smallest common multiple of 18 and 21. The number satisfying the given condition is 126.

### How to Find the LCM of 18 and 21 by Prime Factorization?

To find the LCM of 18 and 21 using prime factorization, we will find the prime factors, (18 = 2 × 3 × 3) and (21 = 3 × 7). LCM of 18 and 21 is the product of prime factors raised to their respective highest exponent among the numbers 18 and 21.⇒ LCM of 18, 21 = 21 × 32 × 71 = 126.

### If the LCM of 21 and 18 is 126, Find its GCF.

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LCM(21, 18) × GCF(21, 18) = 21 × 18Since the LCM of 21 and 18 = 126⇒ 126 × GCF(21, 18) = 378Therefore, the greatest common factor (GCF) = 378/126 = 3.