The number 31891
31891 is the 3426th prime number. Its only divisors are 1 and 31891.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31891: the 3426th prime number.
- 2
31891 is prime, so its only factors are 1 and 31891. It is the 3426th prime; the next prime is 31907 and the one before is 31883.
- 3
The divisors add up to 31892; without 31891 itself that is 1, so 31891 is deficient (1 is less than 31891). Euler's totient φ(31891) = 31890 numbers up to 31891 share no factor with it.
- 4
The digits of 31891 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 59 steps to reach 1.
31891 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 31892 |
| Euler totient φ(n) | 31890 |
| Square | 1017035881 |
| Cube | 32434291280971 |
| Square root | 178.580514 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 59 |
| Scientific notation | 3.1891 × |
31891 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand eight hundred and ninety-one |
| Binary (base 2) | 111110010010011 |
| Octal (base 8) | 76223 |
| Hexadecimal (base 16) | 7C93 |
| Base 3 | 1121202011 |
| As time | 31891 seconds = 8 h 51 min 31 s |
Is 31891 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 3) | 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 31891 a prime number?
Yes. 31891 is divisible only by 1 and itself.
What are the factors of 31891?
1, 31891.
What is 31891 in binary?
111110010010011 (hexadecimal 7C93, octal 76223).
What is the square root of 31891?
About 178.5805.
Is 31891 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 31891?
31891 is the 3426th prime number.