The number 21288
21288 is a composite number with 16 divisors. Its prime factorisation is × 3 × 887. Divisors (16): 1, 2, 3, 4, 6, 8, 12, 24, 887, 1774, 2661, 3548, 5322, 7096, 10644, 21288.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21288 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21288 is composite. Its prime factorisation is
- 3
The divisors add up to 53280; without 21288 itself that is 31992, so 21288 is abundant (31992 is more than 21288). Euler's totient φ(21288) = 7088 numbers up to 21288 share no factor with it.
- 4
The digits of 21288 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 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21288 = 2^{3} \times 3 \times 887 \]21288 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 53280 |
| Euler totient φ(n) | 7088 |
| Square | 453178944 |
| Cube | 9647273359872 |
| Square root | 145.904078 (= 2√5322) |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1288 × |
21288 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and eighty-eight |
| Binary (base 2) | 101001100101000 |
| Octal (base 8) | 51450 |
| Hexadecimal (base 16) | 5328 |
| Base 3 | 1002012110 |
| As time | 21288 seconds = 5 h 54 min 48 s |
Is 21288 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21288 ÷ 2 = 10644) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21288 ÷ 3 = 7096) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21288 ÷ 4 = 5322) | 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 | Yes (21288 ÷ 6 = 3548) | 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 (21288 ÷ 8 = 2661) | 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 8) | 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 (21288 ÷ 12 = 1774) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21288 a prime number?
No. 21288 = × 3 × 887, so it is divisible by 2.
What are the factors of 21288?
1, 2, 3, 4, 6, 8, 12, 24, 887, 1774, 2661, 3548, 5322, 7096, 10644, 21288.
What is 21288 in binary?
101001100101000 (hexadecimal 5328, octal 51450).
What is the square root of 21288?
About 145.9041, exactly 2√5322.
Is 21288 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21288?
It is a composite number with 16 divisors.