The number 81240
81240 is a composite number with 32 divisors. Its prime factorisation is × 3 × 5 × 677. Divisors (32): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120 … 81240.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81240: a Harshad number: divisible by its digit sum 15.
- 2
81240 is composite. Its prime factorisation is
- 3
The divisors add up to 244080; without 81240 itself that is 162840, so 81240 is abundant (162840 is more than 81240). Euler's totient φ(81240) = 21632 numbers up to 81240 share no factor with it.
- 4
The digits of 81240 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 89 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81240 = 2^{3} \times 3 \times 5 \times 677 \]81240 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 244080 |
| Euler totient φ(n) | 21632 |
| Square | 6599937600 |
| Cube | 536178930624000 |
| Square root | 285.026315 (= 2√20310) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 89 |
| Scientific notation | 8.124 × |
81240 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand two hundred and forty |
| Binary (base 2) | 10011110101011000 |
| Octal (base 8) | 236530 |
| Hexadecimal (base 16) | 13D58 |
| Base 3 | 11010102220 |
| As time | 81240 seconds = 22 h 34 min 0 s |
Is 81240 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81240 ÷ 2 = 40620) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (81240 ÷ 3 = 27080) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (81240 ÷ 4 = 20310) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (81240 ÷ 5 = 16248) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (81240 ÷ 6 = 13540) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 (81240 ÷ 8 = 10155) | 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 (81240 ÷ 10 = 8124) | 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 (81240 ÷ 12 = 6770) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81240 a prime number?
No. 81240 = × 3 × 5 × 677, so it is divisible by 2.
What are the factors of 81240?
1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120, 677, 1354, 2031, 2708, 3385, 4062, 5416, 6770, 8124, 10155, 13540, 16248, 20310, 27080, 40620, 81240.
What is 81240 in binary?
10011110101011000 (hexadecimal 13D58, octal 236530).
What is the square root of 81240?
About 285.0263, exactly 2√20310.
Is 81240 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 81240?
81240 is a Harshad number: divisible by its digit sum 15.