Number dictionary · Exact arithmetic
5: factors and number facts
five is an odd number and is prime. Its 2 positive divisors form 1 factor pair.
Number JD Editorial Team · Updated 2026-10-08
- In words
- five
- Roman numeral
- V
- Prime factorization
- 5
- Digital root
- 5
All factors of 5
A positive factor divides 5 with no remainder. In ascending order, the complete list is:
1, 5
Factor pairs
- 1 × 5 = 5
Each pair describes an arrangement of 5 items into equal rows. The pairs have different row and column counts; 5 cannot make a square array of whole items.
Divisor totals
- Positive divisors
- 2
- Sum of all divisors
- 6
- Sum excluding 5
- 1
- Classification
- deficient
5 is deficient because its proper divisors add to 1, which is less than 5.
Prime factorization of 5
5 = 5
Repeated division, step by step
- 5 ÷ 5 = 1
Multiply the prime divisors in these steps to reconstruct 5. Each prime in this factorization occurs once. The divisor-count calculation is (1 + 1) = 2.
The preceding prime is 3. The next larger prime is 7. To check 5 for primality, it is sufficient to test possible divisors from 2 through 2.
Learn the factorization method5 in words, Roman numerals and other bases
| Representation | Value |
|---|---|
| English (US style) | five |
| Roman numeral | V |
| Binary (base 2) | 101 |
| Octal (base 8) | 5 |
| Decimal (base 10) | 5 |
| Hexadecimal (base 16) | 5 |
Check the binary conversion
Read 101 from right to left using place values 1, 2, 4, 8 and successive powers of two. Keep the values whose bit is 1:
4 + 1 = 5
Check the hexadecimal conversion
5 × 16^0 = 5
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 5
- 5 squared
- 5 × 5 = 25
- 5 cubed
- 5 × 5 × 5 = 125
- Square root
- ≈ 2.236068
- Simplified radical
- √5
5 lies between 4 (2²) and 9 (3²), so it is not a perfect square. It is not a perfect cube.
5 is not triangular: no positive whole-number k satisfies k(k + 1) / 2 = 5.
Distinguish a square from a square rootMultiplication table for 5
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 | 2 | 1 | No |
| 3 | 1 | 2 | No |
| 4 | 1 | 1 | No |
| 5 | 1 | 0 | Yes |
| 6 | 0 | 5 | No |
| 7 | 0 | 5 | No |
| 8 | 0 | 5 | No |
| 9 | 0 | 5 | No |
| 10 | 0 | 5 | No |
| 11 | 0 | 5 | No |
| 12 | 0 | 5 | No |
For example, 5 = 7 × 0 + 5. A remainder of zero is what makes a divisor a factor.
Digit sum and digital root of 5
5 contains 1 decimal digit. Its digit sum is 5 = 5.
It already has one digit, so there is no reduction step.
The digital root is 5. 5 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, 5/100 simplifies to 1/20 by dividing both terms by their greatest common divisor, 5. Its decimal value is 0.05.
The greatest common divisor of 5 and 12 is 1. Their least common multiple is 60. The identity GCD × LCM = 5 × 12 = 60 checks both results.
Work through GCF and LCMQuestions about 5
What are the factors of 5?
The positive factors are 1, 5. There are 2 factors, including 1 and 5.
Is 5 a prime number?
Yes. The only positive divisors of 5 are 1 and 5.
How do you write 5 in Roman numerals?
5 is V in standard subtractive Roman numeral notation.
What is the binary representation of 5?
5 in decimal is 101 in base 2. Adding its active place values gives 4 + 1 = 5.
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.