The number 21680
21680 is a composite number with 20 divisors. Its prime factorisation is × 5 × 271. Divisors (20): 1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 271, 542, 1084, 1355, 2168, 2710 … 21680.
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How to work it out
- 1
21680 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21680 is composite. Its prime factorisation is
- 3
The divisors add up to 50592; without 21680 itself that is 28912, so 21680 is abundant (28912 is more than 21680). Euler's totient φ(21680) = 8640 numbers up to 21680 share no factor with it.
- 4
The digits of 21680 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21680 = 2^{4} \times 5 \times 271 \]21680 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 50592 |
| Euler totient φ(n) | 8640 |
| Square | 470022400 |
| Cube | 10190085632000 |
| Square root | 147.241299 (= 4√1355) |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.168 × |
21680 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and eighty |
| Binary (base 2) | 101010010110000 |
| Octal (base 8) | 52260 |
| Hexadecimal (base 16) | 54B0 |
| Base 3 | 1002201222 |
| As time | 21680 seconds = 6 h 1 min 20 s |
Is 21680 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21680 ÷ 2 = 10840) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21680 ÷ 4 = 5420) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21680 ÷ 5 = 4336) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 | Yes (21680 ÷ 8 = 2710) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21680 ÷ 10 = 2168) | 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 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21680 a prime number?
No. 21680 = × 5 × 271, so it is divisible by 2.
What are the factors of 21680?
1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 271, 542, 1084, 1355, 2168, 2710, 4336, 5420, 10840, 21680.
What is 21680 in binary?
101010010110000 (hexadecimal 54B0, octal 52260).
What is the square root of 21680?
About 147.2413, exactly 4√1355.
Is 21680 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 21680?
It is a composite number with 20 divisors.