The number 393
393 is a palindrome: it reads 393 backwards too. Its prime factorisation is 3 × 131. Divisors (4): 1, 3, 131, 393.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 393: a palindrome: it reads 393 backwards too; a semiprime: 3 × 131, the product of two primes.
- 2
393 is composite. Its prime factorisation is
- 3
The divisors add up to 528; without 393 itself that is 135, so 393 is deficient (135 is less than 393). Euler's totient φ(393) = 260 numbers up to 393 share no factor with it.
- 4
The digits of 393 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 58 steps to reach 1.
LaTeX source of the formulas on this page
\[ 393 = 3 \times 131 \]
393 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 528 |
| Euler totient φ(n) | 260 |
| Square | 154449 |
| Cube | 60698457 |
| Square root | 19.824228 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 58 |
| Scientific notation | 3.93 × |
393 in other forms
| Form | Value |
|---|---|
| In words | three hundred and ninety-three |
| Roman numerals | CCCXCIII |
| Binary (base 2) | 110001001 |
| Octal (base 8) | 611 |
| Hexadecimal (base 16) | 189 |
| Base 3 | 112120 |
| As time | 393 seconds = 6 min 33 s |
Is 393 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 (393 ÷ 3 = 131) | 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 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | 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 393 a prime number?
No. 393 = 3 × 131, so it is divisible by 3.
What are the factors of 393?
1, 3, 131, 393.
What is 393 in binary?
110001001 (hexadecimal 189, octal 611).
What is the square root of 393?
About 19.8242.
What is 393 in Roman numerals?
CCCXCIII.
Is 393 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 393?
393 is a palindrome: it reads 393 backwards too; a semiprime: 3 × 131, the product of two primes.