The number 21768
21768 is a composite number with 16 divisors. Its prime factorisation is × 3 × 907. Divisors (16): 1, 2, 3, 4, 6, 8, 12, 24, 907, 1814, 2721, 3628, 5442, 7256, 10884, 21768.
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How to work it out
- 1
What is special about 21768: a Harshad number: divisible by its digit sum 24.
- 2
21768 is composite. Its prime factorisation is
- 3
The divisors add up to 54480; without 21768 itself that is 32712, so 21768 is abundant (32712 is more than 21768). Euler's totient φ(21768) = 7248 numbers up to 21768 share no factor with it.
- 4
The digits of 21768 add up to 24, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21768 = 2^{3} \times 3 \times 907 \]21768 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 54480 |
| Euler totient φ(n) | 7248 |
| Square | 473845824 |
| Cube | 10314675896832 |
| Square root | 147.539825 (= 2√5442) |
| Digit sum / digital root | 24 / 6 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1768 × |
21768 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and sixty-eight |
| Binary (base 2) | 101010100001000 |
| Octal (base 8) | 52410 |
| Hexadecimal (base 16) | 5508 |
| Base 3 | 1002212020 |
| As time | 21768 seconds = 6 h 2 min 48 s |
Is 21768 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21768 ÷ 2 = 10884) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21768 ÷ 3 = 7256) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21768 ÷ 4 = 5442) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21768 ÷ 6 = 3628) | 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 | Yes (21768 ÷ 8 = 2721) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21768 ÷ 12 = 1814) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21768 a prime number?
No. 21768 = × 3 × 907, so it is divisible by 2.
What are the factors of 21768?
1, 2, 3, 4, 6, 8, 12, 24, 907, 1814, 2721, 3628, 5442, 7256, 10884, 21768.
What is 21768 in binary?
101010100001000 (hexadecimal 5508, octal 52410).
What is the square root of 21768?
About 147.5398, exactly 2√5442.
Is 21768 divisible by 3?
Yes. Its digits add up to 24, a multiple of 3.
What is special about the number 21768?
21768 is a Harshad number: divisible by its digit sum 24.