The number 291
291 is a composite number with 4 divisors. Its prime factorisation is 3 × 97. Divisors (4): 1, 3, 97, 291.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 291: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 97, the product of two primes.
- 2
291 is composite. Its prime factorisation is
- 3
The divisors add up to 392; without 291 itself that is 101, so 291 is deficient (101 is less than 291). Euler's totient φ(291) = 192 numbers up to 291 share no factor with it.
- 4
The digits of 291 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 117 steps to reach 1.
LaTeX source of the formulas on this page
\[ 291 = 3 \times 97 \]
291 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 392 |
| Euler totient φ(n) | 192 |
| Square | 84681 |
| Cube | 24642171 |
| Square root | 17.058722 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 117 |
| Scientific notation | 2.91 × |
291 in other forms
| Form | Value |
|---|---|
| In words | two hundred and ninety-one |
| Roman numerals | CCXCI |
| Binary (base 2) | 100100011 |
| Octal (base 8) | 443 |
| Hexadecimal (base 16) | 123 |
| Base 3 | 101210 |
| As time | 291 seconds = 4 min 51 s |
Is 291 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 | Yes (291 ÷ 3 = 97) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 291 a prime number?
No. 291 = 3 × 97, so it is divisible by 3.
What are the factors of 291?
1, 3, 97, 291.
What is 291 in binary?
100100011 (hexadecimal 123, octal 443).
What is the square root of 291?
About 17.0587.
What is 291 in Roman numerals?
CCXCI.
Is 291 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 291?
291 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 97, the product of two primes.