The number 21739
21739 is a twin prime (21737 and 21739 are both prime) and the 2439th prime number. Its only divisors are 1 and 21739.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21739: a twin prime (21737 and 21739 are both prime); the 2439th prime number.
- 2
21739 is prime, so its only factors are 1 and 21739. It is the 2439th prime; the next prime is 21751 and the one before is 21737.
- 3
The divisors add up to 21740; without 21739 itself that is 1, so 21739 is deficient (1 is less than 21739). Euler's totient φ(21739) = 21738 numbers up to 21739 share no factor with it.
- 4
The digits of 21739 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 175 steps to reach 1.
21739 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21740 |
| Euler totient φ(n) | 21738 |
| Square | 472584121 |
| Cube | 10273506206419 |
| Square root | 147.441514 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 175 |
| Scientific notation | 2.1739 × |
21739 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and thirty-nine |
| Binary (base 2) | 101010011101011 |
| Octal (base 8) | 52353 |
| Hexadecimal (base 16) | 54EB |
| Base 3 | 1002211011 |
| As time | 21739 seconds = 6 h 2 min 19 s |
Is 21739 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 4) | 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 4) | 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 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | 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 21739 a prime number?
Yes. 21739 is divisible only by 1 and itself.
What are the factors of 21739?
1, 21739.
What is 21739 in binary?
101010011101011 (hexadecimal 54EB, octal 52353).
What is the square root of 21739?
About 147.4415.
Is 21739 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21739?
21739 is a twin prime (21737 and 21739 are both prime); the 2439th prime number.