Number dictionary · Exact arithmetic
491: factors and number facts
four hundred ninety-one 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
- four hundred ninety-one
- Roman numeral
- CDXCI
- Prime factorization
- 491
- Digital root
- 5
All factors of 491
A positive factor divides 491 with no remainder. In ascending order, the complete list is:
1, 491
Factor pairs
- 1 × 491 = 491
Each pair describes an arrangement of 491 items into equal rows. The pairs have different row and column counts; 491 cannot make a square array of whole items.
Divisor totals
- Positive divisors
- 2
- Sum of all divisors
- 492
- Sum excluding 491
- 1
- Classification
- deficient
491 is deficient because its proper divisors add to 1, which is less than 491.
Prime factorization of 491
491 = 491
Repeated division, step by step
- 491 ÷ 491 = 1
Multiply the prime divisors in these steps to reconstruct 491. Each prime in this factorization occurs once. The divisor-count calculation is (1 + 1) = 2.
The preceding prime is 487. The next larger prime is 499. To check 491 for primality, it is sufficient to test possible divisors from 2 through 22.
Learn the factorization method491 in words, Roman numerals and other bases
| Representation | Value |
|---|---|
| English (US style) | four hundred ninety-one |
| Roman numeral | CDXCI |
| Binary (base 2) | 111101011 |
| Octal (base 8) | 753 |
| Decimal (base 10) | 491 |
| Hexadecimal (base 16) | 1EB |
Check the binary conversion
Read 111101011 from right to left using place values 1, 2, 4, 8 and successive powers of two. Keep the values whose bit is 1:
256 + 128 + 64 + 32 + 8 + 2 + 1 = 491
Check the hexadecimal conversion
1 × 16^2 + 14 × 16^1 + 11 × 16^0 = 491
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 491
- 491 squared
- 491 × 491 = 241,081
- 491 cubed
- 491 × 491 × 491 = 118,370,771
- Square root
- ≈ 22.158520
- Simplified radical
- √491
491 lies between 484 (22²) and 529 (23²), so it is not a perfect square. It is not a perfect cube.
491 is not triangular: no positive whole-number k satisfies k(k + 1) / 2 = 491.
Distinguish a square from a square rootMultiplication table for 491
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 | 245 | 1 | No |
| 3 | 163 | 2 | No |
| 4 | 122 | 3 | No |
| 5 | 98 | 1 | No |
| 6 | 81 | 5 | No |
| 7 | 70 | 1 | No |
| 8 | 61 | 3 | No |
| 9 | 54 | 5 | No |
| 10 | 49 | 1 | No |
| 11 | 44 | 7 | No |
| 12 | 40 | 11 | No |
For example, 491 = 7 × 70 + 1. A remainder of zero is what makes a divisor a factor.
Digit sum and digital root of 491
491 contains 3 decimal digits. Its digit sum is 4 + 9 + 1 = 14.
- 491: 4 + 9 + 1 = 14
- 14: 1 + 4 = 5
The digital root is 5. Reversing its digits gives 194; it is not 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, 491/100 simplifies to 491/100 by dividing both terms by their greatest common divisor, 1. Its decimal value is 4.91. Because the numerator exceeds the denominator, this value is greater than one.
The greatest common divisor of 491 and 12 is 1. Their least common multiple is 5892. The identity GCD × LCM = 491 × 12 = 5892 checks both results.
Work through GCF and LCMQuestions about 491
What are the factors of 491?
The positive factors are 1, 491. There are 2 factors, including 1 and 491.
Is 491 a prime number?
Yes. The only positive divisors of 491 are 1 and 491.
How do you write 491 in Roman numerals?
491 is CDXCI in standard subtractive Roman numeral notation.
What is the binary representation of 491?
491 in decimal is 111101011 in base 2. Adding its active place values gives 256 + 128 + 64 + 32 + 8 + 2 + 1 = 491.
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.
NUMBER JOURNAL / JD
A reflective note on 491
Meaning varies by tradition and personal experience. One sighting is not evidence of what will happen next.
The digits of 491 add to 14. That arithmetic result is separate from the cultural symbolism of the pattern. If this number matters to you, write down what you noticed and choose one grounded action rather than treating the sighting as a prediction.