The number 81421
81421 is the 7967th prime number. Its only divisors are 1 and 81421.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81421: the 7967th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
81421 is prime, so its only factors are 1 and 81421. It is the 7967th prime; the next prime is 81439 and the one before is 81409.
- 3
The divisors add up to 81422; without 81421 itself that is 1, so 81421 is deficient (1 is less than 81421). Euler's totient φ(81421) = 81420 numbers up to 81421 share no factor with it.
- 4
The digits of 81421 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 37 steps to reach 1.
81421 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 81422 |
| Euler totient φ(n) | 81420 |
| Square | 6629379241 |
| Cube | 539770687181461 |
| Square root | 285.343652 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 37 |
| Scientific notation | 8.1421 × |
81421 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand four hundred and twenty-one |
| Binary (base 2) | 10011111000001101 |
| Octal (base 8) | 237015 |
| Hexadecimal (base 16) | 13E0D |
| Base 3 | 11010200121 |
| As time | 81421 seconds = 22 h 37 min 1 s |
Is 81421 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 4) | 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 10) | 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 81421 a prime number?
Yes. 81421 is divisible only by 1 and itself.
What are the factors of 81421?
1, 81421.
What is 81421 in binary?
10011111000001101 (hexadecimal 13E0D, octal 237015).
What is the square root of 81421?
About 285.3437.
Is 81421 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 81421?
81421 is the 7967th prime number; a happy number: repeatedly adding the squares of its digits reaches 1.