The number 818
818 is a palindrome: it reads 818 backwards too. Its prime factorisation is 2 × 409. Divisors (4): 1, 2, 409, 818.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 818: a palindrome: it reads 818 backwards too; a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 409, the product of two primes.
- 2
818 is composite. Its prime factorisation is
- 3
The divisors add up to 1230; without 818 itself that is 412, so 818 is deficient (412 is less than 818). Euler's totient φ(818) = 408 numbers up to 818 share no factor with it.
- 4
The digits of 818 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 41 steps to reach 1.
LaTeX source of the formulas on this page
\[ 818 = 2 \times 409 \]
818 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1230 |
| Euler totient φ(n) | 408 |
| Square | 669124 |
| Cube | 547343432 |
| Square root | 28.600699 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 41 |
| Scientific notation | 8.18 × |
818 in other forms
| Form | Value |
|---|---|
| In words | eight hundred and eighteen |
| Roman numerals | DCCCXVIII |
| Binary (base 2) | 1100110010 |
| Octal (base 8) | 1462 |
| Hexadecimal (base 16) | 332 |
| Base 3 | 1010022 |
| As time | 818 seconds = 13 min 38 s |
Is 818 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (818 ÷ 2 = 409) | 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 2) | 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 2) | 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 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 818 a prime number?
No. 818 = 2 × 409, so it is divisible by 2.
What are the factors of 818?
1, 2, 409, 818.
What is 818 in binary?
1100110010 (hexadecimal 332, octal 1462).
What is the square root of 818?
About 28.6007.
What is 818 in Roman numerals?
DCCCXVIII.
Is 818 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 818?
818 is a palindrome: it reads 818 backwards too; a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 409, the product of two primes.