The number 81020
81020 is a composite number with 12 divisors. Its prime factorisation is × 5 × 4051. Divisors (12): 1, 2, 4, 5, 10, 20, 4051, 8102, 16204, 20255, 40510, 81020.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81020 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81020 is composite. Its prime factorisation is
- 3
The divisors add up to 170184; without 81020 itself that is 89164, so 81020 is abundant (89164 is more than 81020). Euler's totient φ(81020) = 32400 numbers up to 81020 share no factor with it.
- 4
The digits of 81020 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 174 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81020 = 2^{2} \times 5 \times 4051 \]81020 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 170184 |
| Euler totient φ(n) | 32400 |
| Square | 6564240400 |
| Cube | 531834757208000 |
| Square root | 284.640124 (= 2√20255) |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 174 |
| Scientific notation | 8.102 × |
81020 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and twenty |
| Binary (base 2) | 10011110001111100 |
| Octal (base 8) | 236174 |
| Hexadecimal (base 16) | 13C7C |
| Base 3 | 11010010202 |
| As time | 81020 seconds = 22 h 30 min 20 s |
Is 81020 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81020 ÷ 2 = 40510) | 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 | Yes (81020 ÷ 4 = 20255) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (81020 ÷ 5 = 16204) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (81020 ÷ 10 = 8102) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81020 a prime number?
No. 81020 = × 5 × 4051, so it is divisible by 2.
What are the factors of 81020?
1, 2, 4, 5, 10, 20, 4051, 8102, 16204, 20255, 40510, 81020.
What is 81020 in binary?
10011110001111100 (hexadecimal 13C7C, octal 236174).
What is the square root of 81020?
About 284.6401, exactly 2√20255.
Is 81020 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 81020?
It is a composite number with 12 divisors.