The number 81040
81040 is a composite number with 20 divisors. Its prime factorisation is × 5 × 1013. Divisors (20): 1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 1013, 2026, 4052, 5065, 8104, 10130 … 81040.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81040 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81040 is composite. Its prime factorisation is
- 3
The divisors add up to 188604; without 81040 itself that is 107564, so 81040 is abundant (107564 is more than 81040). Euler's totient φ(81040) = 32384 numbers up to 81040 share no factor with it.
- 4
The digits of 81040 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 76 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81040 = 2^{4} \times 5 \times 1013 \]81040 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 188604 |
| Euler totient φ(n) | 32384 |
| Square | 6567481600 |
| Cube | 532228708864000 |
| Square root | 284.675254 (= 4√5065) |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 76 |
| Scientific notation | 8.104 × |
81040 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and forty |
| Binary (base 2) | 10011110010010000 |
| Octal (base 8) | 236220 |
| Hexadecimal (base 16) | 13C90 |
| Base 3 | 11010011111 |
| As time | 81040 seconds = 22 h 30 min 40 s |
Is 81040 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81040 ÷ 2 = 40520) | 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 | Yes (81040 ÷ 4 = 20260) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (81040 ÷ 5 = 16208) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 | Yes (81040 ÷ 8 = 10130) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (81040 ÷ 10 = 8104) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81040 a prime number?
No. 81040 = × 5 × 1013, so it is divisible by 2.
What are the factors of 81040?
1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 1013, 2026, 4052, 5065, 8104, 10130, 16208, 20260, 40520, 81040.
What is 81040 in binary?
10011110010010000 (hexadecimal 13C90, octal 236220).
What is the square root of 81040?
About 284.6753, exactly 4√5065.
Is 81040 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 81040?
It is a composite number with 20 divisors.