The number 6991
6991 is the 899th prime number. Its only divisors are 1 and 6991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 6991: the 899th prime number.
- 2
6991 is prime, so its only factors are 1 and 6991. It is the 899th prime; the next prime is 6997 and the one before is 6983.
- 3
The divisors add up to 6992; without 6991 itself that is 1, so 6991 is deficient (1 is less than 6991). Euler's totient φ(6991) = 6990 numbers up to 6991 share no factor with it.
- 4
The digits of 6991 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 57 steps to reach 1.
6991 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 6992 |
| Euler totient φ(n) | 6990 |
| Square | 48874081 |
| Cube | 341678700271 |
| Square root | 83.612200 |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 57 |
| Scientific notation | 6.991 × |
6991 in other forms
| Form | Value |
|---|---|
| In words | six thousand nine hundred and ninety-one |
| Binary (base 2) | 1101101001111 |
| Octal (base 8) | 15517 |
| Hexadecimal (base 16) | 1B4F |
| Base 3 | 100120221 |
| As time | 6991 seconds = 1 h 56 min 31 s |
Is 6991 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 5) | 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 7) | 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 6) | 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 6991 a prime number?
Yes. 6991 is divisible only by 1 and itself.
What are the factors of 6991?
1, 6991.
What is 6991 in binary?
1101101001111 (hexadecimal 1B4F, octal 15517).
What is the square root of 6991?
About 83.6122.
Is 6991 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 6991?
6991 is the 899th prime number.