The number 78840
78840 is a composite number with 64 divisors. Its prime factorisation is × × 5 × 73. Divisors (64): 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 27, 30 … 78840.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 78840: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 27.
- 2
78840 is composite. Its prime factorisation is
- 3
The divisors add up to 266400; without 78840 itself that is 187560, so 78840 is abundant (187560 is more than 78840). Euler's totient φ(78840) = 20736 numbers up to 78840 share no factor with it.
- 4
The digits of 78840 add up to 27, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 99 steps to reach 1.
LaTeX source of the formulas on this page
\[ 78840 = 2^{3} \times 3^{3} \times 5 \times 73 \]78840 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 64 |
| Sum of divisors | 266400 |
| Euler totient φ(n) | 20736 |
| Square | 6215745600 |
| Cube | 490049383104000 |
| Square root | 280.784615 (= 6√2190) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 99 |
| Scientific notation | 7.884 × |
78840 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand eight hundred and forty |
| Binary (base 2) | 10011001111111000 |
| Octal (base 8) | 231770 |
| Hexadecimal (base 16) | 133F8 |
| Base 3 | 11000011000 |
| As time | 78840 seconds = 21 h 54 min 0 s |
Is 78840 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (78840 ÷ 2 = 39420) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (78840 ÷ 3 = 26280) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (78840 ÷ 4 = 19710) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (78840 ÷ 5 = 15768) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (78840 ÷ 6 = 13140) | 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 (78840 ÷ 8 = 9855) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (78840 ÷ 9 = 8760) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (78840 ÷ 10 = 7884) | 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 (78840 ÷ 12 = 6570) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 78840 a prime number?
No. 78840 = × × 5 × 73, so it is divisible by 2.
What are the factors of 78840?
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 27, 30, 36, 40, 45, 54, 60, 72, 73, 90, 108, 120, 135, 146, 180, 216, 219, 270, 292, 360, 365, 438, 540, 584, 657, 730, 876, 1080, 1095, 1314, 1460, 1752, 1971, 2190, 2628, 2920, 3285, 3942, 4380, 5256, 6570, 7884, 8760, 9855, 13140, 15768, 19710, 26280, 39420, 78840.
What is 78840 in binary?
10011001111111000 (hexadecimal 133F8, octal 231770).
What is the square root of 78840?
About 280.7846, exactly 6√2190.
Is 78840 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 78840?
78840 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 27.