The number 21908
21908 is a composite number with 6 divisors. Its prime factorisation is × 5477. Divisors (6): 1, 2, 4, 5477, 10954, 21908.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21908 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21908 is composite. Its prime factorisation is
- 3
The divisors add up to 38346; without 21908 itself that is 16438, so 21908 is deficient (16438 is less than 21908). Euler's totient φ(21908) = 10952 numbers up to 21908 share no factor with it.
- 4
The digits of 21908 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21908 = 2^{2} \times 5477 \]21908 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 38346 |
| Euler totient φ(n) | 10952 |
| Square | 479960464 |
| Cube | 10514973845312 |
| Square root | 148.013513 (= 2√5477) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1908 × |
21908 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and eight |
| Binary (base 2) | 101010110010100 |
| Octal (base 8) | 52624 |
| Hexadecimal (base 16) | 5594 |
| Base 3 | 1010001102 |
| As time | 21908 seconds = 6 h 5 min 8 s |
Is 21908 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21908 ÷ 2 = 10954) | 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 (21908 ÷ 4 = 5477) | 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 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 2) | 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 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21908 a prime number?
No. 21908 = × 5477, so it is divisible by 2.
What are the factors of 21908?
1, 2, 4, 5477, 10954, 21908.
What is 21908 in binary?
101010110010100 (hexadecimal 5594, octal 52624).
What is the square root of 21908?
About 148.0135, exactly 2√5477.
Is 21908 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 21908?
It is a composite number with 6 divisors.