The number 31808
31808 is a composite number with 28 divisors. Its prime factorisation is × 7 × 71. Divisors (28): 1, 2, 4, 7, 8, 14, 16, 28, 32, 56, 64, 71, 112, 142, 224, 284 … 31808.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
31808 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
31808 is composite. Its prime factorisation is
- 3
The divisors add up to 73152; without 31808 itself that is 41344, so 31808 is abundant (41344 is more than 31808). Euler's totient φ(31808) = 13440 numbers up to 31808 share no factor with it.
- 4
The digits of 31808 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 28 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31808 = 2^{6} \times 7 \times 71 \]31808 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 28 |
| Sum of divisors | 73152 |
| Euler totient φ(n) | 13440 |
| Square | 1011748864 |
| Cube | 32181707866112 |
| Square root | 178.347974 (= 8√497) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 28 |
| Scientific notation | 3.1808 × |
31808 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand eight hundred and eight |
| Binary (base 2) | 111110001000000 |
| Octal (base 8) | 76100 |
| Hexadecimal (base 16) | 7C40 |
| Base 3 | 1121122002 |
| As time | 31808 seconds = 8 h 50 min 8 s |
Is 31808 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (31808 ÷ 2 = 15904) | 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 | Yes (31808 ÷ 4 = 7952) | 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 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (31808 ÷ 7 = 4544) | 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 | Yes (31808 ÷ 8 = 3976) | 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 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31808 a prime number?
No. 31808 = × 7 × 71, so it is divisible by 2.
What are the factors of 31808?
1, 2, 4, 7, 8, 14, 16, 28, 32, 56, 64, 71, 112, 142, 224, 284, 448, 497, 568, 994, 1136, 1988, 2272, 3976, 4544, 7952, 15904, 31808.
What is 31808 in binary?
111110001000000 (hexadecimal 7C40, octal 76100).
What is the square root of 31808?
About 178.3480, exactly 8√497.
Is 31808 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 31808?
It is a composite number with 28 divisors.