The number 81740
81740 is a composite number with 24 divisors. Its prime factorisation is × 5 × 61 × 67. Divisors (24): 1, 2, 4, 5, 10, 20, 61, 67, 122, 134, 244, 268, 305, 335, 610, 670 … 81740.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81740: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 20.
- 2
81740 is composite. Its prime factorisation is
- 3
The divisors add up to 177072; without 81740 itself that is 95332, so 81740 is abundant (95332 is more than 81740). Euler's totient φ(81740) = 31680 numbers up to 81740 share no factor with it.
- 4
The digits of 81740 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 94 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81740 = 2^{2} \times 5 \times 61 \times 67 \]81740 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 177072 |
| Euler totient φ(n) | 31680 |
| Square | 6681427600 |
| Cube | 546139892024000 |
| Square root | 285.902081 (= 2√20435) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 94 |
| Scientific notation | 8.174 × |
81740 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand seven hundred and forty |
| Binary (base 2) | 10011111101001100 |
| Octal (base 8) | 237514 |
| Hexadecimal (base 16) | 13F4C |
| Base 3 | 11011010102 |
| As time | 81740 seconds = 22 h 42 min 20 s |
Is 81740 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81740 ÷ 2 = 40870) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (81740 ÷ 4 = 20435) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (81740 ÷ 5 = 16348) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 | No (remainder 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (81740 ÷ 10 = 8174) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81740 a prime number?
No. 81740 = × 5 × 61 × 67, so it is divisible by 2.
What are the factors of 81740?
1, 2, 4, 5, 10, 20, 61, 67, 122, 134, 244, 268, 305, 335, 610, 670, 1220, 1340, 4087, 8174, 16348, 20435, 40870, 81740.
What is 81740 in binary?
10011111101001100 (hexadecimal 13F4C, octal 237514).
What is the square root of 81740?
About 285.9021, exactly 2√20435.
Is 81740 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 81740?
81740 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 20.