The number 21017
21017 is a twin prime (21017 and 21019 are both prime) and the 2364th prime number. Its only divisors are 1 and 21017.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21017: a twin prime (21017 and 21019 are both prime); the 2364th prime number.
- 2
21017 is prime, so its only factors are 1 and 21017. It is the 2364th prime; the next prime is 21019 and the one before is 21013.
- 3
The divisors add up to 21018; without 21017 itself that is 1, so 21017 is deficient (1 is less than 21017). Euler's totient φ(21017) = 21016 numbers up to 21017 share no factor with it.
- 4
The digits of 21017 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
21017 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21018 |
| Euler totient φ(n) | 21016 |
| Square | 441714289 |
| Cube | 9283509211913 |
| Square root | 144.972411 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1017 × |
21017 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and seventeen |
| Binary (base 2) | 101001000011001 |
| Octal (base 8) | 51031 |
| Hexadecimal (base 16) | 5219 |
| Base 3 | 1001211102 |
| As time | 21017 seconds = 5 h 50 min 17 s |
Is 21017 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 2) | 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 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 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | 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 21017 a prime number?
Yes. 21017 is divisible only by 1 and itself.
What are the factors of 21017?
1, 21017.
What is 21017 in binary?
101001000011001 (hexadecimal 5219, octal 51031).
What is the square root of 21017?
About 144.9724.
Is 21017 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 21017?
21017 is a twin prime (21017 and 21019 are both prime); the 2364th prime number.