The number 20808
20808 is a composite number with 36 divisors. Its prime factorisation is × × . Divisors (36): 1, 2, 3, 4, 6, 8, 9, 12, 17, 18, 24, 34, 36, 51, 68, 72 … 20808.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20808: a Harshad number: divisible by its digit sum 18.
- 2
20808 is composite. Its prime factorisation is
- 3
The divisors add up to 59865; without 20808 itself that is 39057, so 20808 is abundant (39057 is more than 20808). Euler's totient φ(20808) = 6528 numbers up to 20808 share no factor with it.
- 4
The digits of 20808 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 180 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20808 = 2^{3} \times 3^{2} \times 17^{2} \]20808 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 36 |
| Sum of divisors | 59865 |
| Euler totient φ(n) | 6528 |
| Square | 432972864 |
| Cube | 9009299354112 |
| Square root | 144.249783 (= 102√2) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 180 |
| Scientific notation | 2.0808 × |
20808 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand eight hundred and eight |
| Binary (base 2) | 101000101001000 |
| Octal (base 8) | 50510 |
| Hexadecimal (base 16) | 5148 |
| Base 3 | 1001112200 |
| As time | 20808 seconds = 5 h 46 min 48 s |
Is 20808 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (20808 ÷ 2 = 10404) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (20808 ÷ 3 = 6936) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (20808 ÷ 4 = 5202) | 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 (20808 ÷ 6 = 3468) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 (20808 ÷ 8 = 2601) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (20808 ÷ 9 = 2312) | 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 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (20808 ÷ 12 = 1734) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20808 a prime number?
No. 20808 = × × , so it is divisible by 2.
What are the factors of 20808?
1, 2, 3, 4, 6, 8, 9, 12, 17, 18, 24, 34, 36, 51, 68, 72, 102, 136, 153, 204, 289, 306, 408, 578, 612, 867, 1156, 1224, 1734, 2312, 2601, 3468, 5202, 6936, 10404, 20808.
What is 20808 in binary?
101000101001000 (hexadecimal 5148, octal 50510).
What is the square root of 20808?
About 144.2498, exactly 102√2.
Is 20808 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 20808?
20808 is a Harshad number: divisible by its digit sum 18.