The number 21873
21873 is a composite number with 8 divisors. Its prime factorisation is 3 × 23 × 317. Divisors (8): 1, 3, 23, 69, 317, 951, 7291, 21873.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21873 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21873 is composite. Its prime factorisation is
- 3
The divisors add up to 30528; without 21873 itself that is 8655, so 21873 is deficient (8655 is less than 21873). Euler's totient φ(21873) = 13904 numbers up to 21873 share no factor with it.
- 4
The digits of 21873 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21873 = 3 \times 23 \times 317 \]
21873 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 30528 |
| Euler totient φ(n) | 13904 |
| Square | 478428129 |
| Cube | 10464658465617 |
| Square root | 147.895233 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1873 × |
21873 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and seventy-three |
| Binary (base 2) | 101010101110001 |
| Octal (base 8) | 52561 |
| Hexadecimal (base 16) | 5571 |
| Base 3 | 1010000010 |
| As time | 21873 seconds = 6 h 4 min 33 s |
Is 21873 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 | Yes (21873 ÷ 3 = 7291) | 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 3) | 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 3) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21873 a prime number?
No. 21873 = 3 × 23 × 317, so it is divisible by 3.
What are the factors of 21873?
1, 3, 23, 69, 317, 951, 7291, 21873.
What is 21873 in binary?
101010101110001 (hexadecimal 5571, octal 52561).
What is the square root of 21873?
About 147.8952.
Is 21873 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21873?
It is a composite number with 8 divisors.