The number 81321
81321 is a composite number with 4 divisors. Its prime factorisation is 3 × 27107. Divisors (4): 1, 3, 27107, 81321.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81321: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 27107, the product of two primes.
- 2
81321 is composite. Its prime factorisation is
- 3
The divisors add up to 108432; without 81321 itself that is 27111, so 81321 is deficient (27111 is less than 81321). Euler's totient φ(81321) = 54212 numbers up to 81321 share no factor with it.
- 4
The digits of 81321 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 226 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81321 = 3 \times 27107 \]
81321 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 108432 |
| Euler totient φ(n) | 54212 |
| Square | 6613105041 |
| Cube | 537784315039161 |
| Square root | 285.168371 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 226 |
| Scientific notation | 8.1321 × |
81321 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand three hundred and twenty-one |
| Binary (base 2) | 10011110110101001 |
| Octal (base 8) | 236651 |
| Hexadecimal (base 16) | 13DA9 |
| Base 3 | 11010112220 |
| As time | 81321 seconds = 22 h 35 min 21 s |
Is 81321 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 | Yes (81321 ÷ 3 = 27107) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 6) | 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 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81321 a prime number?
No. 81321 = 3 × 27107, so it is divisible by 3.
What are the factors of 81321?
1, 3, 27107, 81321.
What is 81321 in binary?
10011110110101001 (hexadecimal 13DA9, octal 236651).
What is the square root of 81321?
About 285.1684.
Is 81321 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 81321?
81321 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 27107, the product of two primes.