The number 42391
42391 is the 4431st prime number. Its only divisors are 1 and 42391.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 42391: the 4431st prime number.
- 2
42391 is prime, so its only factors are 1 and 42391. It is the 4431st prime; the next prime is 42397 and the one before is 42379.
- 3
The divisors add up to 42392; without 42391 itself that is 1, so 42391 is deficient (1 is less than 42391). Euler's totient φ(42391) = 42390 numbers up to 42391 share no factor with it.
- 4
The digits of 42391 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 57 steps to reach 1.
42391 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 42392 |
| Euler totient φ(n) | 42390 |
| Square | 1796996881 |
| Cube | 76176494782471 |
| Square root | 205.890748 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 57 |
| Scientific notation | 4.2391 × |
42391 in other forms
| Form | Value |
|---|---|
| In words | forty-two thousand three hundred and ninety-one |
| Binary (base 2) | 1010010110010111 |
| Octal (base 8) | 122627 |
| Hexadecimal (base 16) | A597 |
| Base 3 | 2011011001 |
| As time | 42391 seconds = 11 h 46 min 31 s |
Is 42391 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 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 1) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 42391 a prime number?
Yes. 42391 is divisible only by 1 and itself.
What are the factors of 42391?
1, 42391.
What is 42391 in binary?
1010010110010111 (hexadecimal A597, octal 122627).
What is the square root of 42391?
About 205.8907.
Is 42391 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 42391?
42391 is the 4431st prime number.