The number 81989
81989 is a composite number with 4 divisors. Its prime factorisation is 163 × 503. Divisors (4): 1, 163, 503, 81989.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81989: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 163 × 503, the product of two primes.
- 2
81989 is composite. Its prime factorisation is
- 3
The divisors add up to 82656; without 81989 itself that is 667, so 81989 is deficient (667 is less than 81989). Euler's totient φ(81989) = 81324 numbers up to 81989 share no factor with it.
- 4
The digits of 81989 add up to 35, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 151 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81989 = 163 \times 503 \]
81989 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 82656 |
| Euler totient φ(n) | 81324 |
| Square | 6722196121 |
| Cube | 551146137764669 |
| Square root | 286.337214 |
| Digit sum / digital root | 35 / 8 |
| Collatz steps to 1 | 151 |
| Scientific notation | 8.1989 × |
81989 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand nine hundred and eighty-nine |
| Binary (base 2) | 10100000001000101 |
| Octal (base 8) | 240105 |
| Hexadecimal (base 16) | 14045 |
| Base 3 | 11011110122 |
| As time | 81989 seconds = 22 h 46 min 29 s |
Is 81989 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81989 a prime number?
No. 81989 = 163 × 503, so it is divisible by 163.
What are the factors of 81989?
1, 163, 503, 81989.
What is 81989 in binary?
10100000001000101 (hexadecimal 14045, octal 240105).
What is the square root of 81989?
About 286.3372.
Is 81989 divisible by 3?
No. Its digits add up to 35, which is not a multiple of 3.
What is special about the number 81989?
81989 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 163 × 503, the product of two primes.