The number 21168
21168 is a composite number with 60 divisors. Its prime factorisation is × × . Divisors (60): 1, 2, 3, 4, 6, 7, 8, 9, 12, 14, 16, 18, 21, 24, 27, 28 … 21168.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21168: a Harshad number: divisible by its digit sum 18.
- 2
21168 is composite. Its prime factorisation is
- 3
The divisors add up to 70680; without 21168 itself that is 49512, so 21168 is abundant (49512 is more than 21168). Euler's totient φ(21168) = 6048 numbers up to 21168 share no factor with it.
- 4
The digits of 21168 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 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21168 = 2^{4} \times 3^{3} \times 7^{2} \]21168 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 60 |
| Sum of divisors | 70680 |
| Euler totient φ(n) | 6048 |
| Square | 448084224 |
| Cube | 9485046853632 |
| Square root | 145.492268 (= 84√3) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1168 × |
21168 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and sixty-eight |
| Binary (base 2) | 101001010110000 |
| Octal (base 8) | 51260 |
| Hexadecimal (base 16) | 52B0 |
| Base 3 | 1002001000 |
| As time | 21168 seconds = 5 h 52 min 48 s |
Is 21168 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21168 ÷ 2 = 10584) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21168 ÷ 3 = 7056) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21168 ÷ 4 = 5292) | 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 (21168 ÷ 6 = 3528) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21168 ÷ 7 = 3024) | 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 (21168 ÷ 8 = 2646) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21168 ÷ 9 = 2352) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21168 ÷ 12 = 1764) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21168 a prime number?
No. 21168 = × × , so it is divisible by 2.
What are the factors of 21168?
1, 2, 3, 4, 6, 7, 8, 9, 12, 14, 16, 18, 21, 24, 27, 28, 36, 42, 48, 49, 54, 56, 63, 72, 84, 98, 108, 112, 126, 144, 147, 168, 189, 196, 216, 252, 294, 336, 378, 392, 432, 441, 504, 588, 756, 784, 882, 1008, 1176, 1323, 1512, 1764, 2352, 2646, 3024, 3528, 5292, 7056, 10584, 21168.
What is 21168 in binary?
101001010110000 (hexadecimal 52B0, octal 51260).
What is the square root of 21168?
About 145.4923, exactly 84√3.
Is 21168 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21168?
21168 is a Harshad number: divisible by its digit sum 18.