The number 21968
21968 is a composite number with 10 divisors. Its prime factorisation is × 1373. Divisors (10): 1, 2, 4, 8, 16, 1373, 2746, 5492, 10984, 21968.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21968 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21968 is composite. Its prime factorisation is
- 3
The divisors add up to 42594; without 21968 itself that is 20626, so 21968 is deficient (20626 is less than 21968). Euler's totient φ(21968) = 10976 numbers up to 21968 share no factor with it.
- 4
The digits of 21968 add up to 26, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 131 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21968 = 2^{4} \times 1373 \]21968 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 10 |
| Sum of divisors | 42594 |
| Euler totient φ(n) | 10976 |
| Square | 482593024 |
| Cube | 10601603551232 |
| Square root | 148.216059 (= 4√1373) |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1968 × |
21968 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and sixty-eight |
| Binary (base 2) | 101010111010000 |
| Octal (base 8) | 52720 |
| Hexadecimal (base 16) | 55D0 |
| Base 3 | 1010010122 |
| As time | 21968 seconds = 6 h 6 min 8 s |
Is 21968 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21968 ÷ 2 = 10984) | 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 (21968 ÷ 4 = 5492) | 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 2) | 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 (21968 ÷ 8 = 2746) | 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 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | 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 21968 a prime number?
No. 21968 = × 1373, so it is divisible by 2.
What are the factors of 21968?
1, 2, 4, 8, 16, 1373, 2746, 5492, 10984, 21968.
What is 21968 in binary?
101010111010000 (hexadecimal 55D0, octal 52720).
What is the square root of 21968?
About 148.2161, exactly 4√1373.
Is 21968 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 21968?
It is a composite number with 10 divisors.