The number 82721
82721 is a twin prime (82721 and 82723 are both prime) and the 8083rd prime number. Its only divisors are 1 and 82721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 82721: a twin prime (82721 and 82723 are both prime); the 8083rd prime number.
- 2
82721 is prime, so its only factors are 1 and 82721. It is the 8083rd prime; the next prime is 82723 and the one before is 82699.
- 3
The divisors add up to 82722; without 82721 itself that is 1, so 82721 is deficient (1 is less than 82721). Euler's totient φ(82721) = 82720 numbers up to 82721 share no factor with it.
- 4
The digits of 82721 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.
82721 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 82722 |
| Euler totient φ(n) | 82720 |
| Square | 6842763841 |
| Cube | 566040267691361 |
| Square root | 287.612587 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 120 |
| Scientific notation | 8.2721 × |
82721 in other forms
| Form | Value |
|---|---|
| In words | eighty-two thousand seven hundred and twenty-one |
| Binary (base 2) | 10100001100100001 |
| Octal (base 8) | 241441 |
| Hexadecimal (base 16) | 14321 |
| Base 3 | 11012110202 |
| As time | 82721 seconds = 22 h 58 min 41 s |
Is 82721 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 1) | 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 2) | 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 1) | 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 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 82721 a prime number?
Yes. 82721 is divisible only by 1 and itself.
What are the factors of 82721?
1, 82721.
What is 82721 in binary?
10100001100100001 (hexadecimal 14321, octal 241441).
What is the square root of 82721?
About 287.6126.
Is 82721 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 82721?
82721 is a twin prime (82721 and 82723 are both prime); the 8083rd prime number.