The number 9891
9891 is a composite number with 12 divisors. Its prime factorisation is × 7 × 157. Divisors (12): 1, 3, 7, 9, 21, 63, 157, 471, 1099, 1413, 3297, 9891.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
9891 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
9891 is composite. Its prime factorisation is
- 3
The divisors add up to 16432; without 9891 itself that is 6541, so 9891 is deficient (6541 is less than 9891). Euler's totient φ(9891) = 5616 numbers up to 9891 share no factor with it.
- 4
The digits of 9891 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 122 steps to reach 1.
LaTeX source of the formulas on this page
\[ 9891 = 3^{2} \times 7 \times 157 \]9891 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 16432 |
| Euler totient φ(n) | 5616 |
| Square | 97831881 |
| Cube | 967655134971 |
| Square root | 99.453507 (= 3√1099) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 122 |
| Scientific notation | 9.891 × |
9891 in other forms
| Form | Value |
|---|---|
| In words | nine thousand eight hundred and ninety-one |
| Binary (base 2) | 10011010100011 |
| Octal (base 8) | 23243 |
| Hexadecimal (base 16) | 26A3 |
| Base 3 | 111120100 |
| As time | 9891 seconds = 2 h 44 min 51 s |
Is 9891 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 (9891 ÷ 3 = 3297) | 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 | Yes (9891 ÷ 7 = 1413) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (9891 ÷ 9 = 1099) | 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 2) | 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 9891 a prime number?
No. 9891 = × 7 × 157, so it is divisible by 3.
What are the factors of 9891?
1, 3, 7, 9, 21, 63, 157, 471, 1099, 1413, 3297, 9891.
What is 9891 in binary?
10011010100011 (hexadecimal 26A3, octal 23243).
What is the square root of 9891?
About 99.4535, exactly 3√1099.
Is 9891 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 9891?
It is a composite number with 12 divisors.