The number 28704
28704 is a composite number with 48 divisors. Its prime factorisation is × 3 × 13 × 23. Divisors (48): 1, 2, 3, 4, 6, 8, 12, 13, 16, 23, 24, 26, 32, 39, 46, 48 … 28704.
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How to work it out
- 1
What is special about 28704: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
28704 is composite. Its prime factorisation is
- 3
The divisors add up to 84672; without 28704 itself that is 55968, so 28704 is abundant (55968 is more than 28704). Euler's totient φ(28704) = 8448 numbers up to 28704 share no factor with it.
- 4
The digits of 28704 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 72 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28704 = 2^{5} \times 3 \times 13 \times 23 \]28704 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 48 |
| Sum of divisors | 84672 |
| Euler totient φ(n) | 8448 |
| Square | 823919616 |
| Cube | 23649788657664 |
| Square root | 169.422549 (= 4√1794) |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 72 |
| Scientific notation | 2.8704 × |
28704 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand seven hundred and four |
| Binary (base 2) | 111000000100000 |
| Octal (base 8) | 70040 |
| Hexadecimal (base 16) | 7020 |
| Base 3 | 1110101010 |
| As time | 28704 seconds = 7 h 58 min 24 s |
Is 28704 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (28704 ÷ 2 = 14352) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (28704 ÷ 3 = 9568) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (28704 ÷ 4 = 7176) | 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 (28704 ÷ 6 = 4784) | 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 (28704 ÷ 8 = 3588) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (28704 ÷ 12 = 2392) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 28704 a prime number?
No. 28704 = × 3 × 13 × 23, so it is divisible by 2.
What are the factors of 28704?
1, 2, 3, 4, 6, 8, 12, 13, 16, 23, 24, 26, 32, 39, 46, 48, 52, 69, 78, 92, 96, 104, 138, 156, 184, 208, 276, 299, 312, 368, 416, 552, 598, 624, 736, 897, 1104, 1196, 1248, 1794, 2208, 2392, 3588, 4784, 7176, 9568, 14352, 28704.
What is 28704 in binary?
111000000100000 (hexadecimal 7020, octal 70040).
What is the square root of 28704?
About 169.4225, exactly 4√1794.
Is 28704 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 28704?
28704 is a happy number: repeatedly adding the squares of its digits reaches 1.