The number 18731
18731 is the 2138th prime number. Its only divisors are 1 and 18731.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 18731: the 2138th prime number.
- 2
18731 is prime, so its only factors are 1 and 18731. It is the 2138th prime; the next prime is 18743 and the one before is 18719.
- 3
The divisors add up to 18732; without 18731 itself that is 1, so 18731 is deficient (1 is less than 18731). Euler's totient φ(18731) = 18730 numbers up to 18731 share no factor with it.
- 4
The digits of 18731 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 84 steps to reach 1.
18731 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 18732 |
| Euler totient φ(n) | 18730 |
| Square | 350850361 |
| Cube | 6571778111891 |
| Square root | 136.861244 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 84 |
| Scientific notation | 1.8731 × |
18731 in other forms
| Form | Value |
|---|---|
| In words | eighteen thousand seven hundred and thirty-one |
| Binary (base 2) | 100100100101011 |
| Octal (base 8) | 44453 |
| Hexadecimal (base 16) | 492B |
| Base 3 | 221200202 |
| As time | 18731 seconds = 5 h 12 min 11 s |
Is 18731 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 2) | 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 5) | 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 2) | 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 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 18731 a prime number?
Yes. 18731 is divisible only by 1 and itself.
What are the factors of 18731?
1, 18731.
What is 18731 in binary?
100100100101011 (hexadecimal 492B, octal 44453).
What is the square root of 18731?
About 136.8612.
Is 18731 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 18731?
18731 is the 2138th prime number.