The number 28920
28920 is a triangular number: 1 + 2 + … + 240 = 28920. Its prime factorisation is × 3 × 5 × 241. Divisors (32): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120 … 28920.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28920: a triangular number: 1 + 2 + … + 240 = 28920.
- 2
28920 is composite. Its prime factorisation is
- 3
The divisors add up to 87120; without 28920 itself that is 58200, so 28920 is abundant (58200 is more than 28920). Euler's totient φ(28920) = 7680 numbers up to 28920 share no factor with it.
- 4
The digits of 28920 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
\[ 28920 = 2^{3} \times 3 \times 5 \times 241 \]28920 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 87120 |
| Euler totient φ(n) | 7680 |
| Square | 836366400 |
| Cube | 24187716288000 |
| Square root | 170.058813 (= 2√7230) |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 72 |
| Scientific notation | 2.892 × |
28920 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand nine hundred and twenty |
| Binary (base 2) | 111000011111000 |
| Octal (base 8) | 70370 |
| Hexadecimal (base 16) | 70F8 |
| Base 3 | 1110200010 |
| As time | 28920 seconds = 8 h 2 min 0 s |
Is 28920 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (28920 ÷ 2 = 14460) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (28920 ÷ 3 = 9640) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (28920 ÷ 4 = 7230) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (28920 ÷ 5 = 5784) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (28920 ÷ 6 = 4820) | 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 | Yes (28920 ÷ 8 = 3615) | 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 | Yes (28920 ÷ 10 = 2892) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (28920 ÷ 12 = 2410) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 28920 a prime number?
No. 28920 = × 3 × 5 × 241, so it is divisible by 2.
What are the factors of 28920?
1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120, 241, 482, 723, 964, 1205, 1446, 1928, 2410, 2892, 3615, 4820, 5784, 7230, 9640, 14460, 28920.
What is 28920 in binary?
111000011111000 (hexadecimal 70F8, octal 70370).
What is the square root of 28920?
About 170.0588, exactly 2√7230.
Is 28920 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 28920?
28920 is a triangular number: 1 + 2 + … + 240 = 28920.