The number 42181
42181 is a twin prime (42179 and 42181 are both prime) and the 4409th prime number. Its only divisors are 1 and 42181.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 42181: a twin prime (42179 and 42181 are both prime); the 4409th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
42181 is prime, so its only factors are 1 and 42181. It is the 4409th prime; the next prime is 42187 and the one before is 42179.
- 3
The divisors add up to 42182; without 42181 itself that is 1, so 42181 is deficient (1 is less than 42181). Euler's totient φ(42181) = 42180 numbers up to 42181 share no factor with it.
- 4
The digits of 42181 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 150 steps to reach 1.
42181 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 42182 |
| Euler totient φ(n) | 42180 |
| Square | 1779236761 |
| Cube | 75049985815741 |
| Square root | 205.380135 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 150 |
| Scientific notation | 4.2181 × |
42181 in other forms
| Form | Value |
|---|---|
| In words | forty-two thousand one hundred and eighty-one |
| Binary (base 2) | 1010010011000101 |
| Octal (base 8) | 122305 |
| Hexadecimal (base 16) | A4C5 |
| Base 3 | 2010212021 |
| As time | 42181 seconds = 11 h 43 min 1 s |
Is 42181 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 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | 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 7) | 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 42181 a prime number?
Yes. 42181 is divisible only by 1 and itself.
What are the factors of 42181?
1, 42181.
What is 42181 in binary?
1010010011000101 (hexadecimal A4C5, octal 122305).
What is the square root of 42181?
About 205.3801.
Is 42181 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 42181?
42181 is a twin prime (42179 and 42181 are both prime); the 4409th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.