The number 16991
16991 is a composite number with 4 divisors. Its prime factorisation is 13 × 1307. Divisors (4): 1, 13, 1307, 16991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 16991: a semiprime: 13 × 1307, the product of two primes.
- 2
16991 is composite. Its prime factorisation is
- 3
The divisors add up to 18312; without 16991 itself that is 1321, so 16991 is deficient (1321 is less than 16991). Euler's totient φ(16991) = 15672 numbers up to 16991 share no factor with it.
- 4
The digits of 16991 add up to 26, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 84 steps to reach 1.
LaTeX source of the formulas on this page
\[ 16991 = 13 \times 1307 \]
16991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 18312 |
| Euler totient φ(n) | 15672 |
| Square | 288694081 |
| Cube | 4905201130271 |
| Square root | 130.349530 |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 84 |
| Scientific notation | 1.6991 × |
16991 in other forms
| Form | Value |
|---|---|
| In words | sixteen thousand nine hundred and ninety-one |
| Binary (base 2) | 100001001011111 |
| Octal (base 8) | 41137 |
| Hexadecimal (base 16) | 425F |
| Base 3 | 212022022 |
| As time | 16991 seconds = 4 h 43 min 11 s |
Is 16991 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 | No (remainder 2) | 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 7) | 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 16991 a prime number?
No. 16991 = 13 × 1307, so it is divisible by 13.
What are the factors of 16991?
1, 13, 1307, 16991.
What is 16991 in binary?
100001001011111 (hexadecimal 425F, octal 41137).
What is the square root of 16991?
About 130.3495.
Is 16991 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 16991?
16991 is a semiprime: 13 × 1307, the product of two primes.