The number 81988
81988 is a composite number with 12 divisors. Its prime factorisation is × 103 × 199. Divisors (12): 1, 2, 4, 103, 199, 206, 398, 412, 796, 20497, 40994, 81988.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
81988 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
81988 is composite. Its prime factorisation is
- 3
The divisors add up to 145600; without 81988 itself that is 63612, so 81988 is deficient (63612 is less than 81988). Euler's totient φ(81988) = 40392 numbers up to 81988 share no factor with it.
- 4
The digits of 81988 add up to 34, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 151 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81988 = 2^{2} \times 103 \times 199 \]81988 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 145600 |
| Euler totient φ(n) | 40392 |
| Square | 6722032144 |
| Cube | 551125971422272 |
| Square root | 286.335468 (= 2√20497) |
| Digit sum / digital root | 34 / 7 |
| Collatz steps to 1 | 151 |
| Scientific notation | 8.1988 × |
81988 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand nine hundred and eighty-eight |
| Binary (base 2) | 10100000001000100 |
| Octal (base 8) | 240104 |
| Hexadecimal (base 16) | 14044 |
| Base 3 | 11011110121 |
| As time | 81988 seconds = 22 h 46 min 28 s |
Is 81988 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (81988 ÷ 2 = 40994) | 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 (81988 ÷ 4 = 20497) | 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 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | 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 7) | 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 5) | 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 81988 a prime number?
No. 81988 = × 103 × 199, so it is divisible by 2.
What are the factors of 81988?
1, 2, 4, 103, 199, 206, 398, 412, 796, 20497, 40994, 81988.
What is 81988 in binary?
10100000001000100 (hexadecimal 14044, octal 240104).
What is the square root of 81988?
About 286.3355, exactly 2√20497.
Is 81988 divisible by 3?
No. Its digits add up to 34, which is not a multiple of 3.
What is special about the number 81988?
It is a composite number with 12 divisors.