The number 21828
21828 is a composite number with 24 divisors. Its prime factorisation is × 3 × 17 × 107. Divisors (24): 1, 2, 3, 4, 6, 12, 17, 34, 51, 68, 102, 107, 204, 214, 321, 428 … 21828.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21828 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21828 is composite. Its prime factorisation is
- 3
The divisors add up to 54432; without 21828 itself that is 32604, so 21828 is abundant (32604 is more than 21828). Euler's totient φ(21828) = 6784 numbers up to 21828 share no factor with it.
- 4
The digits of 21828 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 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21828 = 2^{2} \times 3 \times 17 \times 107 \]21828 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 54432 |
| Euler totient φ(n) | 6784 |
| Square | 476461584 |
| Cube | 10400203455552 |
| Square root | 147.743020 (= 2√5457) |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1828 × |
21828 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and twenty-eight |
| Binary (base 2) | 101010101000100 |
| Octal (base 8) | 52504 |
| Hexadecimal (base 16) | 5544 |
| Base 3 | 1002221110 |
| As time | 21828 seconds = 6 h 3 min 48 s |
Is 21828 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21828 ÷ 2 = 10914) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21828 ÷ 3 = 7276) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21828 ÷ 4 = 5457) | 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 | Yes (21828 ÷ 6 = 3638) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 4) | 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 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21828 ÷ 12 = 1819) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21828 a prime number?
No. 21828 = × 3 × 17 × 107, so it is divisible by 2.
What are the factors of 21828?
1, 2, 3, 4, 6, 12, 17, 34, 51, 68, 102, 107, 204, 214, 321, 428, 642, 1284, 1819, 3638, 5457, 7276, 10914, 21828.
What is 21828 in binary?
101010101000100 (hexadecimal 5544, octal 52504).
What is the square root of 21828?
About 147.7430, exactly 2√5457.
Is 21828 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21828?
It is a composite number with 24 divisors.