The number 1291
1291 is a twin prime (1289 and 1291 are both prime) and the 210th prime number. Its only divisors are 1 and 1291.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1291: a twin prime (1289 and 1291 are both prime); the 210th prime number.
- 2
1291 is prime, so its only factors are 1 and 1291. It is the 210th prime; the next prime is 1297 and the one before is 1289.
- 3
The divisors add up to 1292; without 1291 itself that is 1, so 1291 is deficient (1 is less than 1291). Euler's totient φ(1291) = 1290 numbers up to 1291 share no factor with it.
- 4
The digits of 1291 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 52 steps to reach 1.
1291 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 1292 |
| Euler totient φ(n) | 1290 |
| Square | 1666681 |
| Cube | 2151685171 |
| Square root | 35.930488 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 52 |
| Scientific notation | 1.291 × |
1291 in other forms
| Form | Value |
|---|---|
| In words | one thousand two hundred and ninety-one |
| Roman numerals | MCCXCI |
| Binary (base 2) | 10100001011 |
| Octal (base 8) | 2413 |
| Hexadecimal (base 16) | 50B |
| Base 3 | 1202211 |
| As time | 1291 seconds = 21 min 31 s |
Is 1291 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 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 4) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1291 a prime number?
Yes. 1291 is divisible only by 1 and itself.
What are the factors of 1291?
1, 1291.
What is 1291 in binary?
10100001011 (hexadecimal 50B, octal 2413).
What is the square root of 1291?
About 35.9305.
What is 1291 in Roman numerals?
MCCXCI.
Is 1291 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 1291?
1291 is a twin prime (1289 and 1291 are both prime); the 210th prime number.