The number 81015
81015 is a composite number with 16 divisors. Its prime factorisation is 3 × 5 × 11 × 491. Divisors (16): 1, 3, 5, 11, 15, 33, 55, 165, 491, 1473, 2455, 5401, 7365, 16203, 27005, 81015.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81015: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 15.
- 2
81015 is composite. Its prime factorisation is
- 3
The divisors add up to 141696; without 81015 itself that is 60681, so 81015 is deficient (60681 is less than 81015). Euler's totient φ(81015) = 39200 numbers up to 81015 share no factor with it.
- 4
The digits of 81015 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 76 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81015 = 3 \times 5 \times 11 \times 491 \]
81015 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 141696 |
| Euler totient φ(n) | 39200 |
| Square | 6563430225 |
| Cube | 531736299678375 |
| Square root | 284.631341 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 76 |
| Scientific notation | 8.1015 × |
81015 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and fifteen |
| Binary (base 2) | 10011110001110111 |
| Octal (base 8) | 236167 |
| Hexadecimal (base 16) | 13C77 |
| Base 3 | 11010010120 |
| As time | 81015 seconds = 22 h 30 min 15 s |
Is 81015 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 (81015 ÷ 3 = 27005) | 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 | Yes (81015 ÷ 5 = 16203) | 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 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 7) | 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 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (81015 ÷ 11 = 7365) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81015 a prime number?
No. 81015 = 3 × 5 × 11 × 491, so it is divisible by 3.
What are the factors of 81015?
1, 3, 5, 11, 15, 33, 55, 165, 491, 1473, 2455, 5401, 7365, 16203, 27005, 81015.
What is 81015 in binary?
10011110001110111 (hexadecimal 13C77, octal 236167).
What is the square root of 81015?
About 284.6313.
Is 81015 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 81015?
81015 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 15.