The number 21804
21804 is a composite number with 24 divisors. Its prime factorisation is × 3 × 23 × 79. Divisors (24): 1, 2, 3, 4, 6, 12, 23, 46, 69, 79, 92, 138, 158, 237, 276, 316 … 21804.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21804 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21804 is composite. Its prime factorisation is
- 3
The divisors add up to 53760; without 21804 itself that is 31956, so 21804 is abundant (31956 is more than 21804). Euler's totient φ(21804) = 6864 numbers up to 21804 share no factor with it.
- 4
The digits of 21804 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21804 = 2^{2} \times 3 \times 23 \times 79 \]21804 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 53760 |
| Euler totient φ(n) | 6864 |
| Square | 475414416 |
| Cube | 10365935926464 |
| Square root | 147.661776 (= 2√5451) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1804 × |
21804 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and four |
| Binary (base 2) | 101010100101100 |
| Octal (base 8) | 52454 |
| Hexadecimal (base 16) | 552C |
| Base 3 | 1002220120 |
| As time | 21804 seconds = 6 h 3 min 24 s |
Is 21804 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21804 ÷ 2 = 10902) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21804 ÷ 3 = 7268) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21804 ÷ 4 = 5451) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21804 ÷ 6 = 3634) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 4) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21804 ÷ 12 = 1817) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21804 a prime number?
No. 21804 = × 3 × 23 × 79, so it is divisible by 2.
What are the factors of 21804?
1, 2, 3, 4, 6, 12, 23, 46, 69, 79, 92, 138, 158, 237, 276, 316, 474, 948, 1817, 3634, 5451, 7268, 10902, 21804.
What is 21804 in binary?
101010100101100 (hexadecimal 552C, octal 52454).
What is the square root of 21804?
About 147.6618, exactly 2√5451.
Is 21804 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21804?
It is a composite number with 24 divisors.