The number 12840
12840 is a composite number with 32 divisors. Its prime factorisation is × 3 × 5 × 107. Divisors (32): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 107 … 12840.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 12840: a Harshad number: divisible by its digit sum 15.
- 2
12840 is composite. Its prime factorisation is
- 3
The divisors add up to 38880; without 12840 itself that is 26040, so 12840 is abundant (26040 is more than 12840). Euler's totient φ(12840) = 3392 numbers up to 12840 share no factor with it.
- 4
The digits of 12840 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 24 steps to reach 1.
LaTeX source of the formulas on this page
\[ 12840 = 2^{3} \times 3 \times 5 \times 107 \]12840 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 38880 |
| Euler totient φ(n) | 3392 |
| Square | 164865600 |
| Cube | 2116874304000 |
| Square root | 113.313724 (= 2√3210) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 24 |
| Scientific notation | 1.284 × |
12840 in other forms
| Form | Value |
|---|---|
| In words | twelve thousand eight hundred and forty |
| Binary (base 2) | 11001000101000 |
| Octal (base 8) | 31050 |
| Hexadecimal (base 16) | 3228 |
| Base 3 | 122121120 |
| As time | 12840 seconds = 3 h 34 min 0 s |
Is 12840 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (12840 ÷ 2 = 6420) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (12840 ÷ 3 = 4280) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (12840 ÷ 4 = 3210) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (12840 ÷ 5 = 2568) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (12840 ÷ 6 = 2140) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 (12840 ÷ 8 = 1605) | 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 | Yes (12840 ÷ 10 = 1284) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (12840 ÷ 12 = 1070) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 12840 a prime number?
No. 12840 = × 3 × 5 × 107, so it is divisible by 2.
What are the factors of 12840?
1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 107, 120, 214, 321, 428, 535, 642, 856, 1070, 1284, 1605, 2140, 2568, 3210, 4280, 6420, 12840.
What is 12840 in binary?
11001000101000 (hexadecimal 3228, octal 31050).
What is the square root of 12840?
About 113.3137, exactly 2√3210.
Is 12840 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 12840?
12840 is a Harshad number: divisible by its digit sum 15.