The number 21493
21493 is a twin prime (21491 and 21493 are both prime) and the 2411th prime number. Its only divisors are 1 and 21493.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21493: a twin prime (21491 and 21493 are both prime); the 2411th prime number.
- 2
21493 is prime, so its only factors are 1 and 21493. It is the 2411th prime; the next prime is 21499 and the one before is 21491.
- 3
The divisors add up to 21494; without 21493 itself that is 1, so 21493 is deficient (1 is less than 21493). Euler's totient φ(21493) = 21492 numbers up to 21493 share no factor with it.
- 4
The digits of 21493 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
21493 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21494 |
| Euler totient φ(n) | 21492 |
| Square | 461949049 |
| Cube | 9928670910157 |
| Square root | 146.604911 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1493 × |
21493 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and ninety-three |
| Binary (base 2) | 101001111110101 |
| Octal (base 8) | 51765 |
| Hexadecimal (base 16) | 53F5 |
| Base 3 | 1002111001 |
| As time | 21493 seconds = 5 h 58 min 13 s |
Is 21493 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 3) | 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 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | 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 21493 a prime number?
Yes. 21493 is divisible only by 1 and itself.
What are the factors of 21493?
1, 21493.
What is 21493 in binary?
101001111110101 (hexadecimal 53F5, octal 51765).
What is the square root of 21493?
About 146.6049.
Is 21493 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 21493?
21493 is a twin prime (21491 and 21493 are both prime); the 2411th prime number.