The number 8
8 is a Fibonacci number and a power of 2 (). Its prime factorisation is . Divisors (4): 1, 2, 4, 8.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 8: a Fibonacci number; a power of 2 ().
- 2
8 is composite. Its prime factorisation is
- 3
The divisors add up to 15; without 8 itself that is 7, so 8 is deficient (7 is less than 8). Euler's totient φ(8) = 4 numbers up to 8 share no factor with it.
- 4
The digits of 8 add up to 8, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 3 steps to reach 1.
LaTeX source of the formulas on this page
\[ 8 = 2^{3} \]8 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 15 |
| Euler totient φ(n) | 4 |
| Square | 64 |
| Cube | 512 |
| Square root | 2.828427 (= 2√2) |
| Digit sum / digital root | 8 / 8 |
| Collatz steps to 1 | 3 |
| Scientific notation | 8 × |
| Perfect power |
8 in other forms
| Form | Value |
|---|---|
| In words | eight |
| Roman numerals | VIII |
| Binary (base 2) | 1000 |
| Octal (base 8) | 10 |
| Hexadecimal (base 16) | 8 |
| Base 3 | 22 |
| As time | 8 seconds |
Is 8 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (8 ÷ 2 = 4) | 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 | Yes (8 ÷ 4 = 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 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 | Yes (8 ÷ 8 = 1) | 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 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 8 a prime number?
No. 8 = , so it is divisible by 2.
What are the factors of 8?
1, 2, 4, 8.
What is 8 in binary?
1000 (hexadecimal 8, octal 10).
What is the square root of 8?
About 2.8284, exactly 2√2.
What is 8 in Roman numerals?
VIII.
Is 8 divisible by 3?
No. Its digits add up to 8, which is not a multiple of 3.
What is special about the number 8?
8 is a Fibonacci number; a power of 2 ().