The number 61391
61391 is a composite number with 4 divisors. Its prime factorisation is 11 × 5581. Divisors (4): 1, 11, 5581, 61391.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 61391: a semiprime: 11 × 5581, the product of two primes.
- 2
61391 is composite. Its prime factorisation is
- 3
The divisors add up to 66984; without 61391 itself that is 5593, so 61391 is deficient (5593 is less than 61391). Euler's totient φ(61391) = 55800 numbers up to 61391 share no factor with it.
- 4
The digits of 61391 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 135 steps to reach 1.
LaTeX source of the formulas on this page
\[ 61391 = 11 \times 5581 \]
61391 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 66984 |
| Euler totient φ(n) | 55800 |
| Square | 3768854881 |
| Cube | 231373769999471 |
| Square root | 247.772073 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 135 |
| Scientific notation | 6.1391 × |
61391 in other forms
| Form | Value |
|---|---|
| In words | sixty-one thousand three hundred and ninety-one |
| Binary (base 2) | 1110111111001111 |
| Octal (base 8) | 167717 |
| Hexadecimal (base 16) | EFCF |
| Base 3 | 10010012202 |
| As time | 61391 seconds = 17 h 3 min 11 s |
Is 61391 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 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 | No (remainder 2) | 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 (61391 ÷ 11 = 5581) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 61391 a prime number?
No. 61391 = 11 × 5581, so it is divisible by 11.
What are the factors of 61391?
1, 11, 5581, 61391.
What is 61391 in binary?
1110111111001111 (hexadecimal EFCF, octal 167717).
What is the square root of 61391?
About 247.7721.
Is 61391 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 61391?
61391 is a semiprime: 11 × 5581, the product of two primes.