The number 28409
28409 is a twin prime (28409 and 28411 are both prime) and the 3091st prime number. Its only divisors are 1 and 28409.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 28409: a twin prime (28409 and 28411 are both prime); the 3091st prime number.
- 2
28409 is prime, so its only factors are 1 and 28409. It is the 3091st prime; the next prime is 28411 and the one before is 28403.
- 3
The divisors add up to 28410; without 28409 itself that is 1, so 28409 is deficient (1 is less than 28409). Euler's totient φ(28409) = 28408 numbers up to 28409 share no factor with it.
- 4
The digits of 28409 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 90 steps to reach 1.
28409 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 28410 |
| Euler totient φ(n) | 28408 |
| Square | 807071281 |
| Cube | 22928088021929 |
| Square root | 168.549696 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 90 |
| Scientific notation | 2.8409 × |
28409 in other forms
| Form | Value |
|---|---|
| In words | twenty-eight thousand four hundred and nine |
| Binary (base 2) | 110111011111001 |
| Octal (base 8) | 67371 |
| Hexadecimal (base 16) | 6EF9 |
| Base 3 | 1102222012 |
| As time | 28409 seconds = 7 h 53 min 29 s |
Is 28409 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 2) | 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 5) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | 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 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 28409 a prime number?
Yes. 28409 is divisible only by 1 and itself.
What are the factors of 28409?
1, 28409.
What is 28409 in binary?
110111011111001 (hexadecimal 6EF9, octal 67371).
What is the square root of 28409?
About 168.5497.
Is 28409 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 28409?
28409 is a twin prime (28409 and 28411 are both prime); the 3091st prime number.