The number 21726
21726 is a composite number with 24 divisors. Its prime factorisation is 2 × × 17 × 71. Divisors (24): 1, 2, 3, 6, 9, 17, 18, 34, 51, 71, 102, 142, 153, 213, 306, 426 … 21726.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21726: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.
- 2
21726 is composite. Its prime factorisation is
- 3
The divisors add up to 50544; without 21726 itself that is 28818, so 21726 is abundant (28818 is more than 21726). Euler's totient φ(21726) = 6720 numbers up to 21726 share no factor with it.
- 4
The digits of 21726 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21726 = 2 \times 3^{2} \times 17 \times 71 \]21726 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 50544 |
| Euler totient φ(n) | 6720 |
| Square | 472019076 |
| Cube | 10255086445176 |
| Square root | 147.397422 (= 3√2414) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1726 × |
21726 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and twenty-six |
| Binary (base 2) | 101010011011110 |
| Octal (base 8) | 52336 |
| Hexadecimal (base 16) | 54DE |
| Base 3 | 1002210200 |
| As time | 21726 seconds = 6 h 2 min 6 s |
Is 21726 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21726 ÷ 2 = 10863) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21726 ÷ 3 = 7242) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21726 ÷ 6 = 3621) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | No (remainder 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21726 ÷ 9 = 2414) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 6) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21726 a prime number?
No. 21726 = 2 × × 17 × 71, so it is divisible by 2.
What are the factors of 21726?
1, 2, 3, 6, 9, 17, 18, 34, 51, 71, 102, 142, 153, 213, 306, 426, 639, 1207, 1278, 2414, 3621, 7242, 10863, 21726.
What is 21726 in binary?
101010011011110 (hexadecimal 54DE, octal 52336).
What is the square root of 21726?
About 147.3974, exactly 3√2414.
Is 21726 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21726?
21726 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.