The number 21636
21636 is a composite number with 18 divisors. Its prime factorisation is × × 601. Divisors (18): 1, 2, 3, 4, 6, 9, 12, 18, 36, 601, 1202, 1803, 2404, 3606, 5409, 7212 … 21636.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21636: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.
- 2
21636 is composite. Its prime factorisation is
- 3
The divisors add up to 54782; without 21636 itself that is 33146, so 21636 is abundant (33146 is more than 21636). Euler's totient φ(21636) = 7200 numbers up to 21636 share no factor with it.
- 4
The digits of 21636 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21636 = 2^{2} \times 3^{2} \times 601 \]21636 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 18 |
| Sum of divisors | 54782 |
| Euler totient φ(n) | 7200 |
| Square | 468116496 |
| Cube | 10128168507456 |
| Square root | 147.091808 (= 6√601) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1636 × |
21636 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and thirty-six |
| Binary (base 2) | 101010010000100 |
| Octal (base 8) | 52204 |
| Hexadecimal (base 16) | 5484 |
| Base 3 | 1002200100 |
| As time | 21636 seconds = 6 h 0 min 36 s |
Is 21636 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21636 ÷ 2 = 10818) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21636 ÷ 3 = 7212) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21636 ÷ 4 = 5409) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21636 ÷ 6 = 3606) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 | Yes (21636 ÷ 9 = 2404) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 6) | 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 | Yes (21636 ÷ 12 = 1803) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21636 a prime number?
No. 21636 = × × 601, so it is divisible by 2.
What are the factors of 21636?
1, 2, 3, 4, 6, 9, 12, 18, 36, 601, 1202, 1803, 2404, 3606, 5409, 7212, 10818, 21636.
What is 21636 in binary?
101010010000100 (hexadecimal 5484, octal 52204).
What is the square root of 21636?
About 147.0918, exactly 6√601.
Is 21636 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21636?
21636 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.