The number 21006
21006 is a composite number with 16 divisors. Its prime factorisation is 2 × × 389. Divisors (16): 1, 2, 3, 6, 9, 18, 27, 54, 389, 778, 1167, 2334, 3501, 7002, 10503, 21006.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21006: a Harshad number: divisible by its digit sum 9.
- 2
21006 is composite. Its prime factorisation is
- 3
The divisors add up to 46800; without 21006 itself that is 25794, so 21006 is abundant (25794 is more than 21006). Euler's totient φ(21006) = 6984 numbers up to 21006 share no factor with it.
- 4
The digits of 21006 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21006 = 2 \times 3^{3} \times 389 \]21006 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 46800 |
| Euler totient φ(n) | 6984 |
| Square | 441252036 |
| Cube | 9268940268216 |
| Square root | 144.934468 (= 3√2334) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1006 × |
21006 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and six |
| Binary (base 2) | 101001000001110 |
| Octal (base 8) | 51016 |
| Hexadecimal (base 16) | 520E |
| Base 3 | 1001211000 |
| As time | 21006 seconds = 5 h 50 min 6 s |
Is 21006 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21006 ÷ 2 = 10503) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21006 ÷ 3 = 7002) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21006 ÷ 6 = 3501) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21006 ÷ 9 = 2334) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 6) | 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 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21006 a prime number?
No. 21006 = 2 × × 389, so it is divisible by 2.
What are the factors of 21006?
1, 2, 3, 6, 9, 18, 27, 54, 389, 778, 1167, 2334, 3501, 7002, 10503, 21006.
What is 21006 in binary?
101001000001110 (hexadecimal 520E, octal 51016).
What is the square root of 21006?
About 144.9345, exactly 3√2334.
Is 21006 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 21006?
21006 is a Harshad number: divisible by its digit sum 9.