Factors of 21
"Factors of a Number" Calculator
What are the Factors of 21?
Answer
Factors of 21:
1, 3, 7, 21
(number 21 has 4 factors)
Factor Pairs of 21
A Factor Pair of number 21 is a combination of two factors which can be multiplied together to equal 21.
List of all possible Factor Pairs of 21:
- 1 × 21 = 21
- 3 × 7 = 21
How to find the Factors of 21
Divide 21 by every whole number from 1 up to 4. Each division without a remainder gives a factor and its pair. There is no point going further: 5 × 5 = 25 is already greater than 21, so any larger divisor would pair with a smaller one you have already checked.
- 21 ÷ 1 = 21 — factors 1 and 21
- 21 ÷ 2 — remainder 1, not a factor
- 21 ÷ 3 = 7 — factors 3 and 7
- 21 ÷ 4 — remainder 1, not a factor
Why 21 has exactly 4 factors
The count follows from the prime factorization: add 1 to each exponent and multiply. Counting the divisors this way needs no trial division at all, however large the number is.
21 = 3 × 7
(1 + 1) × (1 + 1) = 4
Step-by-step factorization: Prime factors of 21.
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See Also
- Prime Number Checker - Find out whether a given number is Prime or not
- Prime Factorization - Prime Factorization Calculator
- Prime Numbers List - List of all Prime Numbers - how many Prime numbers are between
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Factors Table
| Number | Factors |
|---|---|
| 6 | 1, 2, 3, 6 |
| 7 | 1, 7 |
| 8 | 1, 2, 4, 8 |
| 9 | 1, 3, 9 |
| 10 | 1, 2, 5, 10 |
| 11 | 1, 11 |
| 12 | 1, 2, 3, 4, 6, 12 |
| 13 | 1, 13 |
| 14 | 1, 2, 7, 14 |
| 15 | 1, 3, 5, 15 |
| 16 | 1, 2, 4, 8, 16 |
| 17 | 1, 17 |
| 18 | 1, 2, 3, 6, 9, 18 |
| 19 | 1, 19 |
| 20 | 1, 2, 4, 5, 10, 20 |
| 21 | 1, 3, 7, 21 |
| 22 | 1, 2, 11, 22 |
| 23 | 1, 23 |
| 24 | 1, 2, 3, 4, 6, 8, 12, 24 |
| 25 | 1, 5, 25 |
| 26 | 1, 2, 13, 26 |
| 27 | 1, 3, 9, 27 |
| 28 | 1, 2, 4, 7, 14, 28 |
| 29 | 1, 29 |
| 30 | 1, 2, 3, 5, 6, 10, 15, 30 |
| 31 | 1, 31 |
| 32 | 1, 2, 4, 8, 16, 32 |
| 33 | 1, 3, 11, 33 |
| 34 | 1, 2, 17, 34 |
| 35 | 1, 5, 7, 35 |
About "Factors of a Number" Calculator
This calculator will help you find all factors of a given number. For example, it can help you find out what are the Factors of 21? (The answer is: 1, 3, 7, 21). Pick the number (e.g. '21'). After that hit the 'Find' button.
The Factors of a number are numbers that divides initial number evenly, with no remainder
"Factors of a Number" Calculator