The number 71981
71981 is a composite number with 12 divisors. Its prime factorisation is × 13 × 113. Divisors (12): 1, 7, 13, 49, 91, 113, 637, 791, 1469, 5537, 10283, 71981.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
71981 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
71981 is composite. Its prime factorisation is
- 3
The divisors add up to 90972; without 71981 itself that is 18991, so 71981 is deficient (18991 is less than 71981). Euler's totient φ(71981) = 56448 numbers up to 71981 share no factor with it.
- 4
The digits of 71981 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 50 steps to reach 1.
LaTeX source of the formulas on this page
\[ 71981 = 7^{2} \times 13 \times 113 \]71981 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 90972 |
| Euler totient φ(n) | 56448 |
| Square | 5181264361 |
| Cube | 372952589969141 |
| Square root | 268.292751 (= 7√1469) |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 50 |
| Scientific notation | 7.1981 × |
71981 in other forms
| Form | Value |
|---|---|
| In words | seventy-one thousand nine hundred and eighty-one |
| Binary (base 2) | 10001100100101101 |
| Octal (base 8) | 214455 |
| Hexadecimal (base 16) | 1192D |
| Base 3 | 10122201222 |
| As time | 71981 seconds = 19 h 59 min 41 s |
Is 71981 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 1) | 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 | Yes (71981 ÷ 7 = 10283) | 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 5) | 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 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 71981 a prime number?
No. 71981 = × 13 × 113, so it is divisible by 7.
What are the factors of 71981?
1, 7, 13, 49, 91, 113, 637, 791, 1469, 5537, 10283, 71981.
What is 71981 in binary?
10001100100101101 (hexadecimal 1192D, octal 214455).
What is the square root of 71981?
About 268.2928, exactly 7√1469.
Is 71981 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 71981?
It is a composite number with 12 divisors.