The number 81371
81371 is a twin prime (81371 and 81373 are both prime) and the 7963rd prime number. Its only divisors are 1 and 81371.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81371: a twin prime (81371 and 81373 are both prime); the 7963rd prime number.
- 2
81371 is prime, so its only factors are 1 and 81371. It is the 7963rd prime; the next prime is 81373 and the one before is 81359.
- 3
The divisors add up to 81372; without 81371 itself that is 1, so 81371 is deficient (1 is less than 81371). Euler's totient φ(81371) = 81370 numbers up to 81371 share no factor with it.
- 4
The digits of 81371 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 120 steps to reach 1.
81371 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 81372 |
| Euler totient φ(n) | 81370 |
| Square | 6621239641 |
| Cube | 538776890827811 |
| Square root | 285.256025 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 120 |
| Scientific notation | 8.1371 × |
81371 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand three hundred and seventy-one |
| Binary (base 2) | 10011110111011011 |
| Octal (base 8) | 236733 |
| Hexadecimal (base 16) | 13DDB |
| Base 3 | 11010121202 |
| As time | 81371 seconds = 22 h 36 min 11 s |
Is 81371 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 3) | 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 4) | 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 81371 a prime number?
Yes. 81371 is divisible only by 1 and itself.
What are the factors of 81371?
1, 81371.
What is 81371 in binary?
10011110111011011 (hexadecimal 13DDB, octal 236733).
What is the square root of 81371?
About 285.2560.
Is 81371 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 81371?
81371 is a twin prime (81371 and 81373 are both prime); the 7963rd prime number.