The number 12991
12991 is a composite number with 4 divisors. Its prime factorisation is 11 × 1181. Divisors (4): 1, 11, 1181, 12991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 12991: a semiprime: 11 × 1181, the product of two primes.
- 2
12991 is composite. Its prime factorisation is
- 3
The divisors add up to 14184; without 12991 itself that is 1193, so 12991 is deficient (1193 is less than 12991). Euler's totient φ(12991) = 11800 numbers up to 12991 share no factor with it.
- 4
The digits of 12991 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 169 steps to reach 1.
LaTeX source of the formulas on this page
\[ 12991 = 11 \times 1181 \]
12991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 14184 |
| Euler totient φ(n) | 11800 |
| Square | 168766081 |
| Cube | 2192440158271 |
| Square root | 113.978068 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 169 |
| Scientific notation | 1.2991 × |
12991 in other forms
| Form | Value |
|---|---|
| In words | twelve thousand nine hundred and ninety-one |
| Binary (base 2) | 11001010111111 |
| Octal (base 8) | 31277 |
| Hexadecimal (base 16) | 32BF |
| Base 3 | 122211011 |
| As time | 12991 seconds = 3 h 36 min 31 s |
Is 12991 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 | No (remainder 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 4) | 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 (12991 ÷ 11 = 1181) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 12991 a prime number?
No. 12991 = 11 × 1181, so it is divisible by 11.
What are the factors of 12991?
1, 11, 1181, 12991.
What is 12991 in binary?
11001010111111 (hexadecimal 32BF, octal 31277).
What is the square root of 12991?
About 113.9781.
Is 12991 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 12991?
12991 is a semiprime: 11 × 1181, the product of two primes.