The number 2191
2191 is a composite number with 4 divisors. Its prime factorisation is 7 × 313. Divisors (4): 1, 7, 313, 2191.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 2191: a semiprime: 7 × 313, the product of two primes.
- 2
2191 is composite. Its prime factorisation is
- 3
The divisors add up to 2512; without 2191 itself that is 321, so 2191 is deficient (321 is less than 2191). Euler's totient φ(2191) = 1872 numbers up to 2191 share no factor with it.
- 4
The digits of 2191 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 76 steps to reach 1.
LaTeX source of the formulas on this page
\[ 2191 = 7 \times 313 \]
2191 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 2512 |
| Euler totient φ(n) | 1872 |
| Square | 4800481 |
| Cube | 10517853871 |
| Square root | 46.808119 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 76 |
| Scientific notation | 2.191 × |
2191 in other forms
| Form | Value |
|---|---|
| In words | two thousand one hundred and ninety-one |
| Roman numerals | MMCXCI |
| Binary (base 2) | 100010001111 |
| Octal (base 8) | 4217 |
| Hexadecimal (base 16) | 88F |
| Base 3 | 10000011 |
| As time | 2191 seconds = 36 min 31 s |
Is 2191 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 | Yes (2191 ÷ 7 = 313) | 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 | No (remainder 2) | 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 2191 a prime number?
No. 2191 = 7 × 313, so it is divisible by 7.
What are the factors of 2191?
1, 7, 313, 2191.
What is 2191 in binary?
100010001111 (hexadecimal 88F, octal 4217).
What is the square root of 2191?
About 46.8081.
What is 2191 in Roman numerals?
MMCXCI.
Is 2191 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 2191?
2191 is a semiprime: 7 × 313, the product of two primes.