The number 21688
21688 is a composite number with 8 divisors. Its prime factorisation is × 2711. Divisors (8): 1, 2, 4, 8, 2711, 5422, 10844, 21688.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21688 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21688 is composite. Its prime factorisation is
- 3
The divisors add up to 40680; without 21688 itself that is 18992, so 21688 is deficient (18992 is less than 21688). Euler's totient φ(21688) = 10840 numbers up to 21688 share no factor with it.
- 4
The digits of 21688 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21688 = 2^{3} \times 2711 \]21688 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 40680 |
| Euler totient φ(n) | 10840 |
| Square | 470369344 |
| Cube | 10201370332672 |
| Square root | 147.268462 (= 2√5422) |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1688 × |
21688 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and eighty-eight |
| Binary (base 2) | 101010010111000 |
| Octal (base 8) | 52270 |
| Hexadecimal (base 16) | 54B8 |
| Base 3 | 1002202021 |
| As time | 21688 seconds = 6 h 1 min 28 s |
Is 21688 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21688 ÷ 2 = 10844) | 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 | Yes (21688 ÷ 4 = 5422) | 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 4) | 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 | Yes (21688 ÷ 8 = 2711) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | 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 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21688 a prime number?
No. 21688 = × 2711, so it is divisible by 2.
What are the factors of 21688?
1, 2, 4, 8, 2711, 5422, 10844, 21688.
What is 21688 in binary?
101010010111000 (hexadecimal 54B8, octal 52270).
What is the square root of 21688?
About 147.2685, exactly 2√5422.
Is 21688 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 21688?
It is a composite number with 8 divisors.