The number 81331
81331 is the 7958th prime number. Its only divisors are 1 and 81331.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81331: the 7958th prime number.
- 2
81331 is prime, so its only factors are 1 and 81331. It is the 7958th prime; the next prime is 81343 and the one before is 81307.
- 3
The divisors add up to 81332; without 81331 itself that is 1, so 81331 is deficient (1 is less than 81331). Euler's totient φ(81331) = 81330 numbers up to 81331 share no factor with it.
- 4
The digits of 81331 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 89 steps to reach 1.
81331 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 81332 |
| Euler totient φ(n) | 81330 |
| Square | 6614731561 |
| Cube | 537982732587691 |
| Square root | 285.185904 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 89 |
| Scientific notation | 8.1331 × |
81331 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand three hundred and thirty-one |
| Binary (base 2) | 10011110110110011 |
| Octal (base 8) | 236663 |
| Hexadecimal (base 16) | 13DB3 |
| Base 3 | 11010120021 |
| As time | 81331 seconds = 22 h 35 min 31 s |
Is 81331 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 5) | 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 7) | 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 8) | 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 81331 a prime number?
Yes. 81331 is divisible only by 1 and itself.
What are the factors of 81331?
1, 81331.
What is 81331 in binary?
10011110110110011 (hexadecimal 13DB3, octal 236663).
What is the square root of 81331?
About 285.1859.
Is 81331 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 81331?
81331 is the 7958th prime number.