The number 21649
21649 is a twin prime (21647 and 21649 are both prime) and the 2431st prime number. Its only divisors are 1 and 21649.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21649: a twin prime (21647 and 21649 are both prime); the 2431st prime number.
- 2
21649 is prime, so its only factors are 1 and 21649. It is the 2431st prime; the next prime is 21661 and the one before is 21647.
- 3
The divisors add up to 21650; without 21649 itself that is 1, so 21649 is deficient (1 is less than 21649). Euler's totient φ(21649) = 21648 numbers up to 21649 share no factor with it.
- 4
The digits of 21649 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 69 steps to reach 1.
21649 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21650 |
| Euler totient φ(n) | 21648 |
| Square | 468679201 |
| Cube | 10146436022449 |
| Square root | 147.135992 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1649 × |
21649 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and forty-nine |
| Binary (base 2) | 101010010010001 |
| Octal (base 8) | 52221 |
| Hexadecimal (base 16) | 5491 |
| Base 3 | 1002200211 |
| As time | 21649 seconds = 6 h 0 min 49 s |
Is 21649 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 1) | 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 1) | 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 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21649 a prime number?
Yes. 21649 is divisible only by 1 and itself.
What are the factors of 21649?
1, 21649.
What is 21649 in binary?
101010010010001 (hexadecimal 5491, octal 52221).
What is the square root of 21649?
About 147.1360.
Is 21649 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21649?
21649 is a twin prime (21647 and 21649 are both prime); the 2431st prime number.