The number 21567
21567 is a composite number with 16 divisors. Its prime factorisation is 3 × 7 × 13 × 79. Divisors (16): 1, 3, 7, 13, 21, 39, 79, 91, 237, 273, 553, 1027, 1659, 3081, 7189, 21567.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21567: a Harshad number: divisible by its digit sum 21.
- 2
21567 is composite. Its prime factorisation is
- 3
The divisors add up to 35840; without 21567 itself that is 14273, so 21567 is deficient (14273 is less than 21567). Euler's totient φ(21567) = 11232 numbers up to 21567 share no factor with it.
- 4
The digits of 21567 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21567 = 3 \times 7 \times 13 \times 79 \]
21567 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 35840 |
| Euler totient φ(n) | 11232 |
| Square | 465135489 |
| Cube | 10031577091263 |
| Square root | 146.857073 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1567 × |
21567 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and sixty-seven |
| Binary (base 2) | 101010000111111 |
| Octal (base 8) | 52077 |
| Hexadecimal (base 16) | 543F |
| Base 3 | 1002120210 |
| As time | 21567 seconds = 5 h 59 min 27 s |
Is 21567 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21567 ÷ 3 = 7189) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21567 ÷ 7 = 3081) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21567 a prime number?
No. 21567 = 3 × 7 × 13 × 79, so it is divisible by 3.
What are the factors of 21567?
1, 3, 7, 13, 21, 39, 79, 91, 237, 273, 553, 1027, 1659, 3081, 7189, 21567.
What is 21567 in binary?
101010000111111 (hexadecimal 543F, octal 52077).
What is the square root of 21567?
About 146.8571.
Is 21567 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21567?
21567 is a Harshad number: divisible by its digit sum 21.