The number 21109
21109 is a composite number with 8 divisors. Its prime factorisation is 11 × 19 × 101. Divisors (8): 1, 11, 19, 101, 209, 1111, 1919, 21109.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21109 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21109 is composite. Its prime factorisation is
- 3
The divisors add up to 24480; without 21109 itself that is 3371, so 21109 is deficient (3371 is less than 21109). Euler's totient φ(21109) = 18000 numbers up to 21109 share no factor with it.
- 4
The digits of 21109 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21109 = 11 \times 19 \times 101 \]
21109 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 24480 |
| Euler totient φ(n) | 18000 |
| Square | 445589881 |
| Cube | 9405956798029 |
| Square root | 145.289366 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1109 × |
21109 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and nine |
| Binary (base 2) | 101001001110101 |
| Octal (base 8) | 51165 |
| Hexadecimal (base 16) | 5275 |
| Base 3 | 1001221211 |
| As time | 21109 seconds = 5 h 51 min 49 s |
Is 21109 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | 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 1) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21109 ÷ 11 = 1919) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21109 a prime number?
No. 21109 = 11 × 19 × 101, so it is divisible by 11.
What are the factors of 21109?
1, 11, 19, 101, 209, 1111, 1919, 21109.
What is 21109 in binary?
101001001110101 (hexadecimal 5275, octal 51165).
What is the square root of 21109?
About 145.2894.
Is 21109 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21109?
It is a composite number with 8 divisors.