The number 81009
81009 is a composite number with 6 divisors. Its prime factorisation is × 9001. Divisors (6): 1, 3, 9, 9001, 27003, 81009.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81009 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81009 is composite. Its prime factorisation is
- 3
The divisors add up to 117026; without 81009 itself that is 36017, so 81009 is deficient (36017 is less than 81009). Euler's totient φ(81009) = 54000 numbers up to 81009 share no factor with it.
- 4
The digits of 81009 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 45 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81009 = 3^{2} \times 9001 \]81009 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 117026 |
| Euler totient φ(n) | 54000 |
| Square | 6562458081 |
| Cube | 531618166683729 |
| Square root | 284.620800 (= 3√9001) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 45 |
| Scientific notation | 8.1009 × |
81009 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and nine |
| Binary (base 2) | 10011110001110001 |
| Octal (base 8) | 236161 |
| Hexadecimal (base 16) | 13C71 |
| Base 3 | 11010010100 |
| As time | 81009 seconds = 22 h 30 min 9 s |
Is 81009 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (81009 ÷ 3 = 27003) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 | No (remainder 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (81009 ÷ 9 = 9001) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | 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 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81009 a prime number?
No. 81009 = × 9001, so it is divisible by 3.
What are the factors of 81009?
1, 3, 9, 9001, 27003, 81009.
What is 81009 in binary?
10011110001110001 (hexadecimal 13C71, octal 236161).
What is the square root of 81009?
About 284.6208, exactly 3√9001.
Is 81009 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 81009?
It is a composite number with 6 divisors.