The number 891
891 is a binary palindrome (1101111011). Its prime factorisation is × 11. Divisors (10): 1, 3, 9, 11, 27, 33, 81, 99, 297, 891.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 891: a binary palindrome (1101111011).
- 2
891 is composite. Its prime factorisation is
- 3
The divisors add up to 1452; without 891 itself that is 561, so 891 is deficient (561 is less than 891). Euler's totient φ(891) = 540 numbers up to 891 share no factor with it.
- 4
The digits of 891 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 46 steps to reach 1.
LaTeX source of the formulas on this page
\[ 891 = 3^{4} \times 11 \]891 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 10 |
| Sum of divisors | 1452 |
| Euler totient φ(n) | 540 |
| Square | 793881 |
| Cube | 707347971 |
| Square root | 29.849623 (= 9√11) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 46 |
| Scientific notation | 8.91 × |
891 in other forms
| Form | Value |
|---|---|
| In words | eight hundred and ninety-one |
| Roman numerals | DCCCXCI |
| Binary (base 2) | 1101111011 |
| Octal (base 8) | 1573 |
| Hexadecimal (base 16) | 37B |
| Base 3 | 1020000 |
| As time | 891 seconds = 14 min 51 s |
Is 891 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 (891 ÷ 3 = 297) | 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 2) | 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 (891 ÷ 9 = 99) | 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 | Yes (891 ÷ 11 = 81) | 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 891 a prime number?
No. 891 = × 11, so it is divisible by 3.
What are the factors of 891?
1, 3, 9, 11, 27, 33, 81, 99, 297, 891.
What is 891 in binary?
1101111011 (hexadecimal 37B, octal 1573).
What is the square root of 891?
About 29.8496, exactly 9√11.
What is 891 in Roman numerals?
DCCCXCI.
Is 891 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 891?
891 is a binary palindrome (1101111011).