The number 791
791 is a composite number with 4 divisors. Its prime factorisation is 7 × 113. Divisors (4): 1, 7, 113, 791.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 791: a semiprime: 7 × 113, the product of two primes.
- 2
791 is composite. Its prime factorisation is
- 3
The divisors add up to 912; without 791 itself that is 121, so 791 is deficient (121 is less than 791). Euler's totient φ(791) = 672 numbers up to 791 share no factor with it.
- 4
The digits of 791 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 77 steps to reach 1.
LaTeX source of the formulas on this page
\[ 791 = 7 \times 113 \]
791 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 912 |
| Euler totient φ(n) | 672 |
| Square | 625681 |
| Cube | 494913671 |
| Square root | 28.124722 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 77 |
| Scientific notation | 7.91 × |
791 in other forms
| Form | Value |
|---|---|
| In words | seven hundred and ninety-one |
| Roman numerals | DCCXCI |
| Binary (base 2) | 1100010111 |
| Octal (base 8) | 1427 |
| Hexadecimal (base 16) | 317 |
| Base 3 | 1002022 |
| As time | 791 seconds = 13 min 11 s |
Is 791 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (791 ÷ 7 = 113) | 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 7) | 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 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 791 a prime number?
No. 791 = 7 × 113, so it is divisible by 7.
What are the factors of 791?
1, 7, 113, 791.
What is 791 in binary?
1100010111 (hexadecimal 317, octal 1427).
What is the square root of 791?
About 28.1247.
What is 791 in Roman numerals?
DCCXCI.
Is 791 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 791?
791 is a semiprime: 7 × 113, the product of two primes.