The number 28009
28009 is a composite number with 4 divisors. Its prime factorisation is 37 × 757. Divisors (4): 1, 37, 757, 28009.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28009: a semiprime: 37 × 757, the product of two primes.
- 2
28009 is composite. Its prime factorisation is
- 3
The divisors add up to 28804; without 28009 itself that is 795, so 28009 is deficient (795 is less than 28009). Euler's totient φ(28009) = 27216 numbers up to 28009 share no factor with it.
- 4
The digits of 28009 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 134 steps to reach 1.
LaTeX source of the formulas on this page
\[ 28009 = 37 \times 757 \]
28009 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 28804 |
| Euler totient φ(n) | 27216 |
| Square | 784504081 |
| Cube | 21973174804729 |
| Square root | 167.358896 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 134 |
| Scientific notation | 2.8009 × |
28009 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand and nine |
| Binary (base 2) | 110110101101001 |
| Octal (base 8) | 66551 |
| Hexadecimal (base 16) | 6D69 |
| Base 3 | 1102102101 |
| As time | 28009 seconds = 7 h 46 min 49 s |
Is 28009 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 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | 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 3) | 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 28009 a prime number?
No. 28009 = 37 × 757, so it is divisible by 37.
What are the factors of 28009?
1, 37, 757, 28009.
What is 28009 in binary?
110110101101001 (hexadecimal 6D69, octal 66551).
What is the square root of 28009?
About 167.3589.
Is 28009 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 28009?
28009 is a semiprime: 37 × 757, the product of two primes.