GCF for 1 and 21

What is the Greatest Common Factor of 1 and 21?

Answer: GCF of 1 and 21 is 1

(One)

Finding GCF for 1 and 21 using all factors (divisors) listing

The first method to find GCF for numbers 1 and 21 is to list all factors for both numbers and pick the highest common one:

All factors of 1: 1

All factors of 21: 1, 3, 7, 21

So the Greatest Common Factor for 1 and 21 is 1

Finding GCF for 1 and 21 by Prime Factorization

GCF Table

Number 1Number 2GCF
1211
2211
321
4211
5211
621
721
8211
921
1021
1121
1221
1321
1421
1521
1621
1721
1821
19211
2021
212121
22211
23211
24213
25211
26211
27213
28217
29211
30213

About "Greatest Common Factor" Calculator

This calculator will help you find the greatest common factor (GCF) of two numbers. For example, it can help you find out what is the Greatest Common Factor of 1 and 21? (The answer is: 1). Select the first number (e.g. '1') and the second number (e.g. '21'). After that hit the 'Calculate' button.
Greatest Common Factor (GCF) also known as the Greatest Common Divisor (GCD) or Highest Common Factor (HCF) - it is the largest positive integer that divides each of the integers with zero remainder

FAQ

What is the Greatest Common Factor of 1 and 21?

GCF of 1 and 21 is 1