The number 21843
21843 is a composite number with 8 divisors. Its prime factorisation is × 809. Divisors (8): 1, 3, 9, 27, 809, 2427, 7281, 21843.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21843: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21843 is composite. Its prime factorisation is
- 3
The divisors add up to 32400; without 21843 itself that is 10557, so 21843 is deficient (10557 is less than 21843). Euler's totient φ(21843) = 14544 numbers up to 21843 share no factor with it.
- 4
The digits of 21843 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
\[ 21843 = 3^{3} \times 809 \]21843 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 32400 |
| Euler totient φ(n) | 14544 |
| Square | 477116649 |
| Cube | 10421658964107 |
| Square root | 147.793775 (= 3√2427) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.1843 × |
21843 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and forty-three |
| Binary (base 2) | 101010101010011 |
| Octal (base 8) | 52523 |
| Hexadecimal (base 16) | 5553 |
| Base 3 | 1002222000 |
| As time | 21843 seconds = 6 h 4 min 3 s |
Is 21843 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21843 ÷ 3 = 7281) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | 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 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21843 ÷ 9 = 2427) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21843 a prime number?
No. 21843 = × 809, so it is divisible by 3.
What are the factors of 21843?
1, 3, 9, 27, 809, 2427, 7281, 21843.
What is 21843 in binary?
101010101010011 (hexadecimal 5553, octal 52523).
What is the square root of 21843?
About 147.7938, exactly 3√2427.
Is 21843 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21843?
21843 is a happy number: repeatedly adding the squares of its digits reaches 1.