The number 21618
21618 is a composite number with 12 divisors. Its prime factorisation is 2 × × 1201. Divisors (12): 1, 2, 3, 6, 9, 18, 1201, 2402, 3603, 7206, 10809, 21618.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21618: a Harshad number: divisible by its digit sum 18.
- 2
21618 is composite. Its prime factorisation is
- 3
The divisors add up to 46878; without 21618 itself that is 25260, so 21618 is abundant (25260 is more than 21618). Euler's totient φ(21618) = 7200 numbers up to 21618 share no factor with it.
- 4
The digits of 21618 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 69 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21618 = 2 \times 3^{2} \times 1201 \]21618 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 46878 |
| Euler totient φ(n) | 7200 |
| Square | 467337924 |
| Cube | 10102911241032 |
| Square root | 147.030609 (= 3√2402) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 69 |
| Scientific notation | 2.1618 × |
21618 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and eighteen |
| Binary (base 2) | 101010001110010 |
| Octal (base 8) | 52162 |
| Hexadecimal (base 16) | 5472 |
| Base 3 | 1002122200 |
| As time | 21618 seconds = 6 h 0 min 18 s |
Is 21618 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21618 ÷ 2 = 10809) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21618 ÷ 3 = 7206) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | 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 (21618 ÷ 6 = 3603) | 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 | No (remainder 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21618 ÷ 9 = 2402) | 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 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21618 a prime number?
No. 21618 = 2 × × 1201, so it is divisible by 2.
What are the factors of 21618?
1, 2, 3, 6, 9, 18, 1201, 2402, 3603, 7206, 10809, 21618.
What is 21618 in binary?
101010001110010 (hexadecimal 5472, octal 52162).
What is the square root of 21618?
About 147.0306, exactly 3√2402.
Is 21618 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21618?
21618 is a Harshad number: divisible by its digit sum 18.