The number 21708
21708 is a composite number with 30 divisors. Its prime factorisation is × × 67. Divisors (30): 1, 2, 3, 4, 6, 9, 12, 18, 27, 36, 54, 67, 81, 108, 134, 162 … 21708.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21708: a Harshad number: divisible by its digit sum 18.
- 2
21708 is composite. Its prime factorisation is
- 3
The divisors add up to 57596; without 21708 itself that is 35888, so 21708 is abundant (35888 is more than 21708). Euler's totient φ(21708) = 7128 numbers up to 21708 share no factor with it.
- 4
The digits of 21708 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 162 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21708 = 2^{2} \times 3^{4} \times 67 \]21708 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 30 |
| Sum of divisors | 57596 |
| Euler totient φ(n) | 7128 |
| Square | 471237264 |
| Cube | 10229618526912 |
| Square root | 147.336350 (= 18√67) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.1708 × |
21708 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and eight |
| Binary (base 2) | 101010011001100 |
| Octal (base 8) | 52314 |
| Hexadecimal (base 16) | 54CC |
| Base 3 | 1002210000 |
| As time | 21708 seconds = 6 h 1 min 48 s |
Is 21708 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21708 ÷ 2 = 10854) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21708 ÷ 3 = 7236) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21708 ÷ 4 = 5427) | 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 (21708 ÷ 6 = 3618) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21708 ÷ 9 = 2412) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21708 ÷ 12 = 1809) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21708 a prime number?
No. 21708 = × × 67, so it is divisible by 2.
What are the factors of 21708?
1, 2, 3, 4, 6, 9, 12, 18, 27, 36, 54, 67, 81, 108, 134, 162, 201, 268, 324, 402, 603, 804, 1206, 1809, 2412, 3618, 5427, 7236, 10854, 21708.
What is 21708 in binary?
101010011001100 (hexadecimal 54CC, octal 52314).
What is the square root of 21708?
About 147.3363, exactly 18√67.
Is 21708 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21708?
21708 is a Harshad number: divisible by its digit sum 18.