The number 21284
21284 is a composite number with 12 divisors. Its prime factorisation is × 17 × 313. Divisors (12): 1, 2, 4, 17, 34, 68, 313, 626, 1252, 5321, 10642, 21284.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21284: a Harshad number: divisible by its digit sum 17.
- 2
21284 is composite. Its prime factorisation is
- 3
The divisors add up to 39564; without 21284 itself that is 18280, so 21284 is deficient (18280 is less than 21284). Euler's totient φ(21284) = 9984 numbers up to 21284 share no factor with it.
- 4
The digits of 21284 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 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21284 = 2^{2} \times 17 \times 313 \]21284 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 39564 |
| Euler totient φ(n) | 9984 |
| Square | 453008656 |
| Cube | 9641836234304 |
| Square root | 145.890370 (= 2√5321) |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1284 × |
21284 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and eighty-four |
| Binary (base 2) | 101001100100100 |
| Octal (base 8) | 51444 |
| Hexadecimal (base 16) | 5324 |
| Base 3 | 1002012022 |
| As time | 21284 seconds = 5 h 54 min 44 s |
Is 21284 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21284 ÷ 2 = 10642) | 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 (21284 ÷ 4 = 5321) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | 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 4) | 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 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 4) | 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 21284 a prime number?
No. 21284 = × 17 × 313, so it is divisible by 2.
What are the factors of 21284?
1, 2, 4, 17, 34, 68, 313, 626, 1252, 5321, 10642, 21284.
What is 21284 in binary?
101001100100100 (hexadecimal 5324, octal 51444).
What is the square root of 21284?
About 145.8904, exactly 2√5321.
Is 21284 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 21284?
21284 is a Harshad number: divisible by its digit sum 17.