The number 81431
81431 is a composite number with 4 divisors. Its prime factorisation is 7 × 11633. Divisors (4): 1, 7, 11633, 81431.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81431: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 7 × 11633, the product of two primes.
- 2
81431 is composite. Its prime factorisation is
- 3
The divisors add up to 93072; without 81431 itself that is 11641, so 81431 is deficient (11641 is less than 81431). Euler's totient φ(81431) = 69792 numbers up to 81431 share no factor with it.
- 4
The digits of 81431 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 138 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81431 = 7 \times 11633 \]
81431 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 93072 |
| Euler totient φ(n) | 69792 |
| Square | 6631007761 |
| Cube | 539969592985991 |
| Square root | 285.361175 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 138 |
| Scientific notation | 8.1431 × |
81431 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand four hundred and thirty-one |
| Binary (base 2) | 10011111000010111 |
| Octal (base 8) | 237027 |
| Hexadecimal (base 16) | 13E17 |
| Base 3 | 11010200222 |
| As time | 81431 seconds = 22 h 37 min 11 s |
Is 81431 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | 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 | Yes (81431 ÷ 7 = 11633) | 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 7) | 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 1) | 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 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81431 a prime number?
No. 81431 = 7 × 11633, so it is divisible by 7.
What are the factors of 81431?
1, 7, 11633, 81431.
What is 81431 in binary?
10011111000010111 (hexadecimal 13E17, octal 237027).
What is the square root of 81431?
About 285.3612.
Is 81431 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 81431?
81431 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 7 × 11633, the product of two primes.