The number 39721
39721 is a composite number with 8 divisors. Its prime factorisation is 11 × 23 × 157. Divisors (8): 1, 11, 23, 157, 253, 1727, 3611, 39721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
39721 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
39721 is composite. Its prime factorisation is
- 3
The divisors add up to 45504; without 39721 itself that is 5783, so 39721 is deficient (5783 is less than 39721). Euler's totient φ(39721) = 34320 numbers up to 39721 share no factor with it.
- 4
The digits of 39721 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 119 steps to reach 1.
LaTeX source of the formulas on this page
\[ 39721 = 11 \times 23 \times 157 \]
39721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 45504 |
| Euler totient φ(n) | 34320 |
| Square | 1577757841 |
| Cube | 62670119202361 |
| Square root | 199.301279 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 119 |
| Scientific notation | 3.9721 × |
39721 in other forms
| Form | Value |
|---|---|
| In words | thirty-nine thousand seven hundred and twenty-one |
| Binary (base 2) | 1001101100101001 |
| Octal (base 8) | 115451 |
| Hexadecimal (base 16) | 9B29 |
| Base 3 | 2000111011 |
| As time | 39721 seconds = 11 h 2 min 1 s |
Is 39721 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 1) | 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 1) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | 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 | Yes (39721 ÷ 11 = 3611) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 39721 a prime number?
No. 39721 = 11 × 23 × 157, so it is divisible by 11.
What are the factors of 39721?
1, 11, 23, 157, 253, 1727, 3611, 39721.
What is 39721 in binary?
1001101100101001 (hexadecimal 9B29, octal 115451).
What is the square root of 39721?
About 199.3013.
Is 39721 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 39721?
It is a composite number with 8 divisors.