The number 28440
28440 is a composite number with 48 divisors. Its prime factorisation is × × 5 × 79. Divisors (48): 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36 … 28440.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28440: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.
- 2
28440 is composite. Its prime factorisation is
- 3
The divisors add up to 93600; without 28440 itself that is 65160, so 28440 is abundant (65160 is more than 28440). Euler's totient φ(28440) = 7488 numbers up to 28440 share no factor with it.
- 4
The digits of 28440 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 121 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28440 = 2^{3} \times 3^{2} \times 5 \times 79 \]28440 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 48 |
| Sum of divisors | 93600 |
| Euler totient φ(n) | 7488 |
| Square | 808833600 |
| Cube | 23003227584000 |
| Square root | 168.641632 (= 6√790) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 121 |
| Scientific notation | 2.844 × |
28440 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand four hundred and forty |
| Binary (base 2) | 110111100011000 |
| Octal (base 8) | 67430 |
| Hexadecimal (base 16) | 6F18 |
| Base 3 | 1110000100 |
| As time | 28440 seconds = 7 h 54 min 0 s |
Is 28440 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (28440 ÷ 2 = 14220) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (28440 ÷ 3 = 9480) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (28440 ÷ 4 = 7110) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (28440 ÷ 5 = 5688) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (28440 ÷ 6 = 4740) | 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 | Yes (28440 ÷ 8 = 3555) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (28440 ÷ 9 = 3160) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (28440 ÷ 10 = 2844) | 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 (28440 ÷ 12 = 2370) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 28440 a prime number?
No. 28440 = × × 5 × 79, so it is divisible by 2.
What are the factors of 28440?
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 79, 90, 120, 158, 180, 237, 316, 360, 395, 474, 632, 711, 790, 948, 1185, 1422, 1580, 1896, 2370, 2844, 3160, 3555, 4740, 5688, 7110, 9480, 14220, 28440.
What is 28440 in binary?
110111100011000 (hexadecimal 6F18, octal 67430).
What is the square root of 28440?
About 168.6416, exactly 6√790.
Is 28440 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 28440?
28440 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.