The number 81002
81002 is a composite number with 8 divisors. Its prime factorisation is 2 × 101 × 401. Divisors (8): 1, 2, 101, 202, 401, 802, 40501, 81002.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81002 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81002 is composite. Its prime factorisation is
- 3
The divisors add up to 123012; without 81002 itself that is 42010, so 81002 is deficient (42010 is less than 81002). Euler's totient φ(81002) = 40000 numbers up to 81002 share no factor with it.
- 4
The digits of 81002 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 45 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81002 = 2 \times 101 \times 401 \]
81002 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 123012 |
| Euler totient φ(n) | 40000 |
| Square | 6561324004 |
| Cube | 531480366972008 |
| Square root | 284.608503 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 45 |
| Scientific notation | 8.1002 × |
81002 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and two |
| Binary (base 2) | 10011110001101010 |
| Octal (base 8) | 236152 |
| Hexadecimal (base 16) | 13C6A |
| Base 3 | 11010010002 |
| As time | 81002 seconds = 22 h 30 min 2 s |
Is 81002 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81002 ÷ 2 = 40501) | 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 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 5) | 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 | No (remainder 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 2) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81002 a prime number?
No. 81002 = 2 × 101 × 401, so it is divisible by 2.
What are the factors of 81002?
1, 2, 101, 202, 401, 802, 40501, 81002.
What is 81002 in binary?
10011110001101010 (hexadecimal 13C6A, octal 236152).
What is the square root of 81002?
About 284.6085.
Is 81002 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 81002?
It is a composite number with 8 divisors.