The number 81401
81401 is the 7965th prime number. Its only divisors are 1 and 81401.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81401: the 7965th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
81401 is prime, so its only factors are 1 and 81401. It is the 7965th prime; the next prime is 81409 and the one before is 81373.
- 3
The divisors add up to 81402; without 81401 itself that is 1, so 81401 is deficient (1 is less than 81401). Euler's totient φ(81401) = 81400 numbers up to 81401 share no factor with it.
- 4
The digits of 81401 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 89 steps to reach 1.
81401 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 81402 |
| Euler totient φ(n) | 81400 |
| Square | 6626122801 |
| Cube | 539373022124201 |
| Square root | 285.308605 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 89 |
| Scientific notation | 8.1401 × |
81401 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand four hundred and one |
| Binary (base 2) | 10011110111111001 |
| Octal (base 8) | 236771 |
| Hexadecimal (base 16) | 13DF9 |
| Base 3 | 11010122212 |
| As time | 81401 seconds = 22 h 36 min 41 s |
Is 81401 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 5) | 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 5) | 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 1) | 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 81401 a prime number?
Yes. 81401 is divisible only by 1 and itself.
What are the factors of 81401?
1, 81401.
What is 81401 in binary?
10011110111111001 (hexadecimal 13DF9, octal 236771).
What is the square root of 81401?
About 285.3086.
Is 81401 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 81401?
81401 is the 7965th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.