The number 13991
13991 is a composite number with 4 divisors. Its prime factorisation is 17 × 823. Divisors (4): 1, 17, 823, 13991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 13991: a semiprime: 17 × 823, the product of two primes.
- 2
13991 is composite. Its prime factorisation is
- 3
The divisors add up to 14832; without 13991 itself that is 841, so 13991 is deficient (841 is less than 13991). Euler's totient φ(13991) = 13152 numbers up to 13991 share no factor with it.
- 4
The digits of 13991 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 89 steps to reach 1.
LaTeX source of the formulas on this page
\[ 13991 = 17 \times 823 \]
13991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 14832 |
| Euler totient φ(n) | 13152 |
| Square | 195748081 |
| Cube | 2738711401271 |
| Square root | 118.283558 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 89 |
| Scientific notation | 1.3991 × |
13991 in other forms
| Form | Value |
|---|---|
| In words | thirteen thousand nine hundred and ninety-one |
| Binary (base 2) | 11011010100111 |
| Octal (base 8) | 33247 |
| Hexadecimal (base 16) | 36A7 |
| Base 3 | 201012012 |
| As time | 13991 seconds = 3 h 53 min 11 s |
Is 13991 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 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 5) | 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 13991 a prime number?
No. 13991 = 17 × 823, so it is divisible by 17.
What are the factors of 13991?
1, 17, 823, 13991.
What is 13991 in binary?
11011010100111 (hexadecimal 36A7, octal 33247).
What is the square root of 13991?
About 118.2836.
Is 13991 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 13991?
13991 is a semiprime: 17 × 823, the product of two primes.