Number dictionary · Exact arithmetic
8: factors and number facts
eight is an even number and is composite. Its 4 positive divisors form 2 factor pairs.
Number JD Editorial Team · Updated 2026-10-08
- In words
- eight
- Roman numeral
- VIII
- Prime factorization
- 2^3
- Digital root
- 8
All factors of 8
A positive factor divides 8 with no remainder. In ascending order, the complete list is:
1, 2, 4, 8
Factor pairs
- 1 × 8 = 8
- 2 × 4 = 8
Each pair describes an arrangement of 8 items into equal rows. The pairs have different row and column counts; 8 cannot make a square array of whole items.
Divisor totals
- Positive divisors
- 4
- Sum of all divisors
- 15
- Sum excluding 8
- 7
- Classification
- deficient
8 is deficient because its proper divisors add to 7, which is less than 8.
Prime factorization of 8
8 = 2^3
Repeated division, step by step
- 8 ÷ 2 = 4
- 4 ÷ 2 = 2
- 2 ÷ 2 = 1
Multiply the prime divisors in these steps to reconstruct 8. An exponent records how many times the same prime occurs. The divisor-count calculation is (3 + 1) = 4.
The preceding prime is 7. The next larger prime is 11. The factor list above explains why 8 is composite.
Learn the factorization method8 in words, Roman numerals and other bases
| Representation | Value |
|---|---|
| English (US style) | eight |
| Roman numeral | VIII |
| Binary (base 2) | 1000 |
| Octal (base 8) | 10 |
| Decimal (base 10) | 8 |
| Hexadecimal (base 16) | 8 |
Check the binary conversion
Read 1000 from right to left using place values 1, 2, 4, 8 and successive powers of two. Keep the values whose bit is 1:
8 = 8
Check the hexadecimal conversion
8 × 16^0 = 8
Hexadecimal uses A through F for digit values 10 through 15. These notations represent the same quantity; changing the base does not change the integer.
Square, cube and square root of 8
- 8 squared
- 8 × 8 = 64
- 8 cubed
- 8 × 8 × 8 = 512
- Square root
- ≈ 2.828427
- Simplified radical
- 2√2
8 lies between 4 (2²) and 9 (3²), so it is not a perfect square. It is also a perfect cube: 2³ = 8.
8 is not triangular: no positive whole-number k satisfies k(k + 1) / 2 = 8.
Distinguish a square from a square rootMultiplication table for 8
These are the first twelve positive multiples. Unlike the finite factor list, the sequence of multiples continues without an upper limit.
Divisibility checks
| Divide by | Whole quotient | Remainder | Divides exactly? |
|---|---|---|---|
| 2 | 4 | 0 | Yes |
| 3 | 2 | 2 | No |
| 4 | 2 | 0 | Yes |
| 5 | 1 | 3 | No |
| 6 | 1 | 2 | No |
| 7 | 1 | 1 | No |
| 8 | 1 | 0 | Yes |
| 9 | 0 | 8 | No |
| 10 | 0 | 8 | No |
| 11 | 0 | 8 | No |
| 12 | 0 | 8 | No |
For example, 8 = 7 × 1 + 1. A remainder of zero is what makes a divisor a factor.
Digit sum and digital root of 8
8 contains 1 decimal digit. Its digit sum is 8 = 8.
It already has one digit, so there is no reduction step.
The digital root is 8. 8 reads the same forward and backward, making it a decimal palindrome. Digit patterns depend on the notation being used.
Digital-root arithmetic always finishes at a single digit for a positive integer. Some numerology methods stop at 11, 22 or 33 instead; that is a separate interpretive convention.
Fractions and a worked comparison
As a fraction of 100, 8/100 simplifies to 2/25 by dividing both terms by their greatest common divisor, 4. Its decimal value is 0.08.
The greatest common divisor of 8 and 12 is 4. Their least common multiple is 24. The identity GCD × LCM = 8 × 12 = 96 checks both results.
Work through GCF and LCMQuestions about 8
What are the factors of 8?
The positive factors are 1, 2, 4, 8. There are 4 factors, including 1 and 8.
Is 8 a prime number?
No. 8 is composite: 2^3 = 8.
How do you write 8 in Roman numerals?
8 is VIII in standard subtractive Roman numeral notation.
What is the binary representation of 8?
8 in decimal is 1000 in base 2. Adding its active place values gives 8 = 8.
Methods and reference definitions
Number JD calculates each result from the integer on this page. Positive factors are enumerated in pairs; repeated division gives the prime factorization; place values verify base conversions. Decimal square roots are rounded to six places when irrational.