The number 71721
71721 is a composite number with 12 divisors. Its prime factorisation is × 13 × 613. Divisors (12): 1, 3, 9, 13, 39, 117, 613, 1839, 5517, 7969, 23907, 71721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
71721 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
71721 is composite. Its prime factorisation is
- 3
The divisors add up to 111748; without 71721 itself that is 40027, so 71721 is deficient (40027 is less than 71721). Euler's totient φ(71721) = 44064 numbers up to 71721 share no factor with it.
- 4
The digits of 71721 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 174 steps to reach 1.
LaTeX source of the formulas on this page
\[ 71721 = 3^{2} \times 13 \times 613 \]71721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 111748 |
| Euler totient φ(n) | 44064 |
| Square | 5143901841 |
| Cube | 368925783938361 |
| Square root | 267.807767 (= 3√7969) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 174 |
| Scientific notation | 7.1721 × |
71721 in other forms
| Form | Value |
|---|---|
| In words | seventy-one thousand seven hundred and twenty-one |
| Binary (base 2) | 10001100000101001 |
| Octal (base 8) | 214051 |
| Hexadecimal (base 16) | 11829 |
| Base 3 | 10122101100 |
| As time | 71721 seconds = 19 h 55 min 21 s |
Is 71721 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 (71721 ÷ 3 = 23907) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (71721 ÷ 9 = 7969) | 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 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 71721 a prime number?
No. 71721 = × 13 × 613, so it is divisible by 3.
What are the factors of 71721?
1, 3, 9, 13, 39, 117, 613, 1839, 5517, 7969, 23907, 71721.
What is 71721 in binary?
10001100000101001 (hexadecimal 11829, octal 214051).
What is the square root of 71721?
About 267.8078, exactly 3√7969.
Is 71721 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 71721?
It is a composite number with 12 divisors.