The number 21684
21684 is a composite number with 24 divisors. Its prime factorisation is × 3 × 13 × 139. Divisors (24): 1, 2, 3, 4, 6, 12, 13, 26, 39, 52, 78, 139, 156, 278, 417, 556 … 21684.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21684 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21684 is composite. Its prime factorisation is
- 3
The divisors add up to 54880; without 21684 itself that is 33196, so 21684 is abundant (33196 is more than 21684). Euler's totient φ(21684) = 6624 numbers up to 21684 share no factor with it.
- 4
The digits of 21684 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 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21684 = 2^{2} \times 3 \times 13 \times 139 \]21684 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 54880 |
| Euler totient φ(n) | 6624 |
| Square | 470195856 |
| Cube | 10195726941504 |
| Square root | 147.254881 (= 2√5421) |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1684 × |
21684 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and eighty-four |
| Binary (base 2) | 101010010110100 |
| Octal (base 8) | 52264 |
| Hexadecimal (base 16) | 54B4 |
| Base 3 | 1002202010 |
| As time | 21684 seconds = 6 h 1 min 24 s |
Is 21684 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21684 ÷ 2 = 10842) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21684 ÷ 3 = 7228) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21684 ÷ 4 = 5421) | 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 | Yes (21684 ÷ 6 = 3614) | 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 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 4) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21684 ÷ 12 = 1807) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21684 a prime number?
No. 21684 = × 3 × 13 × 139, so it is divisible by 2.
What are the factors of 21684?
1, 2, 3, 4, 6, 12, 13, 26, 39, 52, 78, 139, 156, 278, 417, 556, 834, 1668, 1807, 3614, 5421, 7228, 10842, 21684.
What is 21684 in binary?
101010010110100 (hexadecimal 54B4, octal 52264).
What is the square root of 21684?
About 147.2549, exactly 2√5421.
Is 21684 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21684?
It is a composite number with 24 divisors.