The number 81018
81018 is a palindrome: it reads 81018 backwards too. Its prime factorisation is 2 × × 7 × 643. Divisors (24): 1, 2, 3, 6, 7, 9, 14, 18, 21, 42, 63, 126, 643, 1286, 1929, 3858 … 81018.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81018: a palindrome: it reads 81018 backwards too; a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.
- 2
81018 is composite. Its prime factorisation is
- 3
The divisors add up to 200928; without 81018 itself that is 119910, so 81018 is abundant (119910 is more than 81018). Euler's totient φ(81018) = 23112 numbers up to 81018 share no factor with it.
- 4
The digits of 81018 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 138 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81018 = 2 \times 3^{2} \times 7 \times 643 \]81018 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 200928 |
| Euler totient φ(n) | 23112 |
| Square | 6563916324 |
| Cube | 531795372737832 |
| Square root | 284.636610 (= 3√9002) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 138 |
| Scientific notation | 8.1018 × |
81018 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and eighteen |
| Binary (base 2) | 10011110001111010 |
| Octal (base 8) | 236172 |
| Hexadecimal (base 16) | 13C7A |
| Base 3 | 11010010200 |
| As time | 81018 seconds = 22 h 30 min 18 s |
Is 81018 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81018 ÷ 2 = 40509) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (81018 ÷ 3 = 27006) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (81018 ÷ 6 = 13503) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (81018 ÷ 7 = 11574) | 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 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (81018 ÷ 9 = 9002) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | 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 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81018 a prime number?
No. 81018 = 2 × × 7 × 643, so it is divisible by 2.
What are the factors of 81018?
1, 2, 3, 6, 7, 9, 14, 18, 21, 42, 63, 126, 643, 1286, 1929, 3858, 4501, 5787, 9002, 11574, 13503, 27006, 40509, 81018.
What is 81018 in binary?
10011110001111010 (hexadecimal 13C7A, octal 236172).
What is the square root of 81018?
About 284.6366, exactly 3√9002.
Is 81018 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 81018?
81018 is a palindrome: it reads 81018 backwards too; a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.