The number 21108
21108 is a composite number with 12 divisors. Its prime factorisation is × 3 × 1759. Divisors (12): 1, 2, 3, 4, 6, 12, 1759, 3518, 5277, 7036, 10554, 21108.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21108: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 12.
- 2
21108 is composite. Its prime factorisation is
- 3
The divisors add up to 49280; without 21108 itself that is 28172, so 21108 is abundant (28172 is more than 21108). Euler's totient φ(21108) = 7032 numbers up to 21108 share no factor with it.
- 4
The digits of 21108 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21108 = 2^{2} \times 3 \times 1759 \]21108 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 49280 |
| Euler totient φ(n) | 7032 |
| Square | 445547664 |
| Cube | 9404620091712 |
| Square root | 145.285925 (= 2√5277) |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1108 × |
21108 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and eight |
| Binary (base 2) | 101001001110100 |
| Octal (base 8) | 51164 |
| Hexadecimal (base 16) | 5274 |
| Base 3 | 1001221210 |
| As time | 21108 seconds = 5 h 51 min 48 s |
Is 21108 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21108 ÷ 2 = 10554) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21108 ÷ 3 = 7036) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21108 ÷ 4 = 5277) | 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 (21108 ÷ 6 = 3518) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 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 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21108 ÷ 12 = 1759) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21108 a prime number?
No. 21108 = × 3 × 1759, so it is divisible by 2.
What are the factors of 21108?
1, 2, 3, 4, 6, 12, 1759, 3518, 5277, 7036, 10554, 21108.
What is 21108 in binary?
101001001110100 (hexadecimal 5274, octal 51164).
What is the square root of 21108?
About 145.2859, exactly 2√5277.
Is 21108 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 21108?
21108 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 12.