The number 309
309 is a composite number with 4 divisors. Its prime factorisation is 3 × 103. Divisors (4): 1, 3, 103, 309.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 309: a semiprime: 3 × 103, the product of two primes.
- 2
309 is composite. Its prime factorisation is
- 3
The divisors add up to 416; without 309 itself that is 107, so 309 is deficient (107 is less than 309). Euler's totient φ(309) = 204 numbers up to 309 share no factor with it.
- 4
The digits of 309 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 24 steps to reach 1.
LaTeX source of the formulas on this page
\[ 309 = 3 \times 103 \]
309 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 416 |
| Euler totient φ(n) | 204 |
| Square | 95481 |
| Cube | 29503629 |
| Square root | 17.578396 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 24 |
| Scientific notation | 3.09 × |
309 in other forms
| Form | Value |
|---|---|
| In words | three hundred and nine |
| Roman numerals | CCCIX |
| Binary (base 2) | 100110101 |
| Octal (base 8) | 465 |
| Hexadecimal (base 16) | 135 |
| Base 3 | 102110 |
| As time | 309 seconds = 5 min 9 s |
Is 309 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 (309 ÷ 3 = 103) | 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 1) | 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 3) | 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 1) | 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 309 a prime number?
No. 309 = 3 × 103, so it is divisible by 3.
What are the factors of 309?
1, 3, 103, 309.
What is 309 in binary?
100110101 (hexadecimal 135, octal 465).
What is the square root of 309?
About 17.5784.
What is 309 in Roman numerals?
CCCIX.
Is 309 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 309?
309 is a semiprime: 3 × 103, the product of two primes.