The number 81025
81025 is a composite number with 12 divisors. Its prime factorisation is × 7 × 463. Divisors (12): 1, 5, 7, 25, 35, 175, 463, 2315, 3241, 11575, 16205, 81025.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81025: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
81025 is composite. Its prime factorisation is
- 3
The divisors add up to 115072; without 81025 itself that is 34047, so 81025 is deficient (34047 is less than 81025). Euler's totient φ(81025) = 55440 numbers up to 81025 share no factor with it.
- 4
The digits of 81025 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 76 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81025 = 5^{2} \times 7 \times 463 \]81025 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 115072 |
| Euler totient φ(n) | 55440 |
| Square | 6565050625 |
| Cube | 531933226890625 |
| Square root | 284.648907 (= 5√3241) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 76 |
| Scientific notation | 8.1025 × |
81025 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and twenty-five |
| Binary (base 2) | 10011110010000001 |
| Octal (base 8) | 236201 |
| Hexadecimal (base 16) | 13C81 |
| Base 3 | 11010010221 |
| As time | 81025 seconds = 22 h 30 min 25 s |
Is 81025 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 | Yes (81025 ÷ 5 = 16205) | 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 | Yes (81025 ÷ 7 = 11575) | 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 7) | 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 | 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 81025 a prime number?
No. 81025 = × 7 × 463, so it is divisible by 5.
What are the factors of 81025?
1, 5, 7, 25, 35, 175, 463, 2315, 3241, 11575, 16205, 81025.
What is 81025 in binary?
10011110010000001 (hexadecimal 13C81, octal 236201).
What is the square root of 81025?
About 284.6489, exactly 5√3241.
Is 81025 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 81025?
81025 is a happy number: repeatedly adding the squares of its digits reaches 1.