The number 81008
81008 is a composite number with 20 divisors. Its prime factorisation is × 61 × 83. Divisors (20): 1, 2, 4, 8, 16, 61, 83, 122, 166, 244, 332, 488, 664, 976, 1328, 5063 … 81008.
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How to work it out
- 1
What is special about 81008: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
81008 is composite. Its prime factorisation is
- 3
The divisors add up to 161448; without 81008 itself that is 80440, so 81008 is deficient (80440 is less than 81008). Euler's totient φ(81008) = 39360 numbers up to 81008 share no factor with it.
- 4
The digits of 81008 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 138 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81008 = 2^{4} \times 61 \times 83 \]81008 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 161448 |
| Euler totient φ(n) | 39360 |
| Square | 6562296064 |
| Cube | 531598479552512 |
| Square root | 284.619044 (= 4√5063) |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 138 |
| Scientific notation | 8.1008 × |
81008 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and eight |
| Binary (base 2) | 10011110001110000 |
| Octal (base 8) | 236160 |
| Hexadecimal (base 16) | 13C70 |
| Base 3 | 11010010022 |
| As time | 81008 seconds = 22 h 30 min 8 s |
Is 81008 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81008 ÷ 2 = 40504) | 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 (81008 ÷ 4 = 20252) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | 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 4) | 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 (81008 ÷ 8 = 10126) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | 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 81008 a prime number?
No. 81008 = × 61 × 83, so it is divisible by 2.
What are the factors of 81008?
1, 2, 4, 8, 16, 61, 83, 122, 166, 244, 332, 488, 664, 976, 1328, 5063, 10126, 20252, 40504, 81008.
What is 81008 in binary?
10011110001110000 (hexadecimal 13C70, octal 236160).
What is the square root of 81008?
About 284.6190, exactly 4√5063.
Is 81008 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 81008?
81008 is a happy number: repeatedly adding the squares of its digits reaches 1.