LCM for 7 and 21
"Least Common Multiple" Calculator
What's the Least Common Multiple (LCM) of 7 and 21?
Answer: LCM of 7 and 21 is 21
(Twenty-one)
Finding LCM for 7 and 21 using GCF's of these numbers
The first method to find LCM for numbers 7 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:
LCM = (Number1 × Number2) ÷ GCF
GCF of numbers 7 and 21 is 7, so
LCM = (7 × 21) ÷ 7
LCM = 147 ÷ 7
LCM = 21
Finding LCM for 7 and 21 by Listing Multiples
The second method to find LCM for numbers 7 and 21 is to list out the common multiples for both nubmers and pick the first which matching:
Multiples of 7: 7, 14, 21, 28, 35
Multiples of 21: 21, 42, 63, 84, 105, [...], 21
So the LCM for 7 and 21 is 21
Finding LCM for 7 and 21 by Prime Factorization
Another method to find LCM for numbers 7 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors:
All Prime Factors of 7: 7 (exponent form: 71)
All Prime Factors of 21: 3, 7 (exponent form: 31, 71)
71 × 31 = 21
Related Calculations
See Also
- Greatest Common Factor - Find the Greatest Common Factor (GCF) of two numbers
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About "Least Common Multiple" Calculator
This calculator will help you find the Least Common Multiple (LCM) of two numbers. For example, it can help you find out what's the Least Common Multiple (LCM) of 7 and 21? (The answer is: 21). Select the first number (e.g. '7') and the second number (e.g. '21'). After that hit the 'Calculate' button.
Least Common Multiple (LCM) also known as the Lowest Common Multiple or Smallest Common Multiple of 2 numbers - it is the smallest positive integer that is divisible by both numbers