The number 19809
19809 is a composite number with 12 divisors. Its prime factorisation is × 31 × 71. Divisors (12): 1, 3, 9, 31, 71, 93, 213, 279, 639, 2201, 6603, 19809.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
19809 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
19809 is composite. Its prime factorisation is
- 3
The divisors add up to 29952; without 19809 itself that is 10143, so 19809 is deficient (10143 is less than 19809). Euler's totient φ(19809) = 12600 numbers up to 19809 share no factor with it.
- 4
The digits of 19809 add up to 27, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 136 steps to reach 1.
LaTeX source of the formulas on this page
\[ 19809 = 3^{2} \times 31 \times 71 \]19809 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 29952 |
| Euler totient φ(n) | 12600 |
| Square | 392396481 |
| Cube | 7772981892129 |
| Square root | 140.744449 (= 3√2201) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 136 |
| Scientific notation | 1.9809 × |
19809 in other forms
| Form | Value |
|---|---|
| In words | nineteen thousand eight hundred and nine |
| Binary (base 2) | 100110101100001 |
| Octal (base 8) | 46541 |
| Hexadecimal (base 16) | 4D61 |
| Base 3 | 1000011200 |
| As time | 19809 seconds = 5 h 30 min 9 s |
Is 19809 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 | Yes (19809 ÷ 3 = 6603) | 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 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (19809 ÷ 9 = 2201) | 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 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 19809 a prime number?
No. 19809 = × 31 × 71, so it is divisible by 3.
What are the factors of 19809?
1, 3, 9, 31, 71, 93, 213, 279, 639, 2201, 6603, 19809.
What is 19809 in binary?
100110101100001 (hexadecimal 4D61, octal 46541).
What is the square root of 19809?
About 140.7444, exactly 3√2201.
Is 19809 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 19809?
It is a composite number with 12 divisors.