The number 61721
61721 is a composite number with 8 divisors. Its prime factorisation is 11 × 31 × 181. Divisors (8): 1, 11, 31, 181, 341, 1991, 5611, 61721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 61721: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
61721 is composite. Its prime factorisation is
- 3
The divisors add up to 69888; without 61721 itself that is 8167, so 61721 is deficient (8167 is less than 61721). Euler's totient φ(61721) = 54000 numbers up to 61721 share no factor with it.
- 4
The digits of 61721 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 179 steps to reach 1.
LaTeX source of the formulas on this page
\[ 61721 = 11 \times 31 \times 181 \]
61721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 69888 |
| Euler totient φ(n) | 54000 |
| Square | 3809481841 |
| Cube | 235125028708361 |
| Square root | 248.437115 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 179 |
| Scientific notation | 6.1721 × |
61721 in other forms
| Form | Value |
|---|---|
| In words | sixty-one thousand seven hundred and twenty-one |
| Binary (base 2) | 1111000100011001 |
| Octal (base 8) | 170431 |
| Hexadecimal (base 16) | F119 |
| Base 3 | 10010122222 |
| As time | 61721 seconds = 17 h 8 min 41 s |
Is 61721 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 | No (remainder 2) | 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 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 | Yes (61721 ÷ 11 = 5611) | 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 61721 a prime number?
No. 61721 = 11 × 31 × 181, so it is divisible by 11.
What are the factors of 61721?
1, 11, 31, 181, 341, 1991, 5611, 61721.
What is 61721 in binary?
1111000100011001 (hexadecimal F119, octal 170431).
What is the square root of 61721?
About 248.4371.
Is 61721 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 61721?
61721 is a happy number: repeatedly adding the squares of its digits reaches 1.