The number 8991
8991 is a composite number with 12 divisors. Its prime factorisation is × 37. Divisors (12): 1, 3, 9, 27, 37, 81, 111, 243, 333, 999, 2997, 8991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 8991: a Harshad number: divisible by its digit sum 27.
- 2
8991 is composite. Its prime factorisation is
- 3
The divisors add up to 13832; without 8991 itself that is 4841, so 8991 is deficient (4841 is less than 8991). Euler's totient φ(8991) = 5832 numbers up to 8991 share no factor with it.
- 4
The digits of 8991 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 140 steps to reach 1.
LaTeX source of the formulas on this page
\[ 8991 = 3^{5} \times 37 \]8991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 13832 |
| Euler totient φ(n) | 5832 |
| Square | 80838081 |
| Cube | 726815186271 |
| Square root | 94.820884 (= 9√111) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 140 |
| Scientific notation | 8.991 × |
8991 in other forms
| Form | Value |
|---|---|
| In words | eight thousand nine hundred and ninety-one |
| Binary (base 2) | 10001100011111 |
| Octal (base 8) | 21437 |
| Hexadecimal (base 16) | 231F |
| Base 3 | 110100000 |
| As time | 8991 seconds = 2 h 29 min 51 s |
Is 8991 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 (8991 ÷ 3 = 2997) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | 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 3) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (8991 ÷ 9 = 999) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 8991 a prime number?
No. 8991 = × 37, so it is divisible by 3.
What are the factors of 8991?
1, 3, 9, 27, 37, 81, 111, 243, 333, 999, 2997, 8991.
What is 8991 in binary?
10001100011111 (hexadecimal 231F, octal 21437).
What is the square root of 8991?
About 94.8209, exactly 9√111.
Is 8991 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 8991?
8991 is a Harshad number: divisible by its digit sum 27.