The number 21019
21019 is a twin prime (21017 and 21019 are both prime) and the 2365th prime number. Its only divisors are 1 and 21019.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21019: a twin prime (21017 and 21019 are both prime); the 2365th prime number.
- 2
21019 is prime, so its only factors are 1 and 21019. It is the 2365th prime; the next prime is 21023 and the one before is 21017.
- 3
The divisors add up to 21020; without 21019 itself that is 1, so 21019 is deficient (1 is less than 21019). Euler's totient φ(21019) = 21018 numbers up to 21019 share no factor with it.
- 4
The digits of 21019 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
21019 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21020 |
| Euler totient φ(n) | 21018 |
| Square | 441798361 |
| Cube | 9286159749859 |
| Square root | 144.979309 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1019 × |
21019 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and nineteen |
| Binary (base 2) | 101001000011011 |
| Octal (base 8) | 51033 |
| Hexadecimal (base 16) | 521B |
| Base 3 | 1001211111 |
| As time | 21019 seconds = 5 h 50 min 19 s |
Is 21019 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 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 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 9) | 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 21019 a prime number?
Yes. 21019 is divisible only by 1 and itself.
What are the factors of 21019?
1, 21019.
What is 21019 in binary?
101001000011011 (hexadecimal 521B, octal 51033).
What is the square root of 21019?
About 144.9793.
Is 21019 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21019?
21019 is a twin prime (21017 and 21019 are both prime); the 2365th prime number.