The number 1191
1191 is a composite number with 4 divisors. Its prime factorisation is 3 × 397. Divisors (4): 1, 3, 397, 1191.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1191: a semiprime: 3 × 397, the product of two primes.
- 2
1191 is composite. Its prime factorisation is
- 3
The divisors add up to 1592; without 1191 itself that is 401, so 1191 is deficient (401 is less than 1191). Euler's totient φ(1191) = 792 numbers up to 1191 share no factor with it.
- 4
The digits of 1191 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 49 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1191 = 3 \times 397 \]
1191 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1592 |
| Euler totient φ(n) | 792 |
| Square | 1418481 |
| Cube | 1689410871 |
| Square root | 34.510868 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 49 |
| Scientific notation | 1.191 × |
1191 in other forms
| Form | Value |
|---|---|
| In words | one thousand one hundred and ninety-one |
| Roman numerals | MCXCI |
| Binary (base 2) | 10010100111 |
| Octal (base 8) | 2247 |
| Hexadecimal (base 16) | 4A7 |
| Base 3 | 1122010 |
| As time | 1191 seconds = 19 min 51 s |
Is 1191 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 (1191 ÷ 3 = 397) | 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 1) | 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 | No (remainder 3) | 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 3) | 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 1191 a prime number?
No. 1191 = 3 × 397, so it is divisible by 3.
What are the factors of 1191?
1, 3, 397, 1191.
What is 1191 in binary?
10010100111 (hexadecimal 4A7, octal 2247).
What is the square root of 1191?
About 34.5109.
What is 1191 in Roman numerals?
MCXCI.
Is 1191 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 1191?
1191 is a semiprime: 3 × 397, the product of two primes.