Factors of 21 | Factor Pairs, Prime Factorization & Divisors

📊 Total Factors: 4
🔢 Prime Factors: 3, 7
✅ Number Type: Composite Number

What Are the Factors of 21?

The factors of 21 are 1, 3, 7, 21. A factor is a whole number that divides 21 exactly without leaving a remainder. These factors can be used to simplify fractions, solve math problems, and understand number relationships.

How to Find the Factors of 21

To find the factors of 21, divide the number by whole numbers starting from 1. If the result is a whole number with no remainder, that divisor is a factor.

21 ÷ 1 = 21
21 ÷ 3 = 7
21 ÷ 7 = 3
21 ÷ 21 = 1

Is 21 Divisible by Other Numbers?

A number is divisible by another number if the division leaves no remainder.

❌ 21 is not divisible by 2
✅ 21 is divisible by 3
❌ 21 is not divisible by 4
❌ 21 is not divisible by 5
❌ 21 is not divisible by 6
✅ 21 is divisible by 7
❌ 21 is not divisible by 8
❌ 21 is not divisible by 9
❌ 21 is not divisible by 10

Real-Life Uses of Factors of 21

Factors of 21 are useful in mathematics, grouping objects, simplifying fractions, finding dimensions of rectangles, and solving division problems. Understanding factors helps students build a strong foundation in arithmetic and number theory.

All Factors of 21

1, 3, 7, 21

Factor Pairs of 21

• 1 × 21
• 3 × 7

Prime Factorization of 21

21 = 3 × 7

Worked Example: Finding Factors of 21

Step 1: Start testing numbers from 1 up to 21.

Step 2: Check which numbers divide 21 without leaving a remainder.

Step 3: The successful divisions are:

21 ÷ 1 = 21 (No remainder)
21 ÷ 3 = 7 (No remainder)
21 ÷ 7 = 3 (No remainder)
21 ÷ 21 = 1 (No remainder)

Answer: Therefore, the factors of 21 are 1, 3, 7, 21.

Number Facts Table

Property	Value
Number	21
Total Factors	4
Largest Factor	21
Smallest Factor	1
Prime Factors	3, 7
Even / Odd	Odd
Prime / Composite	Composite
Perfect Square	No
Perfect Cube	No

Properties of 21

Even or Odd: Odd Number

Prime or Composite: Composite Number

Perfect Square: No

Perfect Cube: No

Unique Prime Factors: 3, 7

Interesting Facts About 21

• 21 is a composite number because it has more than two factors.
• 21 is an odd number.
• The prime factorization of 21 is 3 × 7.
• 21 has 4 total factors.

Is 21 Prime or Composite?

21 is a composite number because it has 4 factors.

Related Factors Pages

Factors of 16
Factors of 17
Factors of 18
Factors of 19
Factors of 20
Factors of 22
Factors of 23
Factors of 24
Factors of 25
Factors of 26

Factoring Calculator

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Frequently Asked Questions

What are the factors of 21?
1, 3, 7, 21

How many factors does 21 have?
4

Is 21 a prime number?
No

What is the largest factor of 21?
21

What is the smallest factor of 21?
1

What are the prime factors of 21?
3, 7

Is 21 even or odd?
Odd

What is the factor pair of 21?
1 × 21, 3 × 7