The number 71991
71991 is a composite number with 12 divisors. Its prime factorisation is × 19 × 421. Divisors (12): 1, 3, 9, 19, 57, 171, 421, 1263, 3789, 7999, 23997, 71991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
71991 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
71991 is composite. Its prime factorisation is
- 3
The divisors add up to 109720; without 71991 itself that is 37729, so 71991 is deficient (37729 is less than 71991). Euler's totient φ(71991) = 45360 numbers up to 71991 share no factor with it.
- 4
The digits of 71991 add up to 27, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 94 steps to reach 1.
LaTeX source of the formulas on this page
\[ 71991 = 3^{2} \times 19 \times 421 \]71991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 109720 |
| Euler totient φ(n) | 45360 |
| Square | 5182704081 |
| Cube | 373108049495271 |
| Square root | 268.311386 (= 3√7999) |
| Digit sum / digital root | 27 / 9 |
| Collatz steps to 1 | 94 |
| Scientific notation | 7.1991 × |
71991 in other forms
| Form | Value |
|---|---|
| In words | seventy-one thousand nine hundred and ninety-one |
| Binary (base 2) | 10001100100110111 |
| Octal (base 8) | 214467 |
| Hexadecimal (base 16) | 11937 |
| Base 3 | 10122202100 |
| As time | 71991 seconds = 19 h 59 min 51 s |
Is 71991 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 (71991 ÷ 3 = 23997) | 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 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (71991 ÷ 9 = 7999) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 71991 a prime number?
No. 71991 = × 19 × 421, so it is divisible by 3.
What are the factors of 71991?
1, 3, 9, 19, 57, 171, 421, 1263, 3789, 7999, 23997, 71991.
What is 71991 in binary?
10001100100110111 (hexadecimal 11937, octal 214467).
What is the square root of 71991?
About 268.3114, exactly 3√7999.
Is 71991 divisible by 3?
Yes. Its digits add up to 27, a multiple of 3.
What is special about the number 71991?
It is a composite number with 12 divisors.