The number 31881
31881 is a composite number with 4 divisors. Its prime factorisation is 3 × 10627. Divisors (4): 1, 3, 10627, 31881.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31881: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10627, the product of two primes.
- 2
31881 is composite. Its prime factorisation is
- 3
The divisors add up to 42512; without 31881 itself that is 10631, so 31881 is deficient (10631 is less than 31881). Euler's totient φ(31881) = 21252 numbers up to 31881 share no factor with it.
- 4
The digits of 31881 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 178 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31881 = 3 \times 10627 \]
31881 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 42512 |
| Euler totient φ(n) | 21252 |
| Square | 1016398161 |
| Cube | 32403789770841 |
| Square root | 178.552513 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 178 |
| Scientific notation | 3.1881 × |
31881 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand eight hundred and eighty-one |
| Binary (base 2) | 111110010001001 |
| Octal (base 8) | 76211 |
| Hexadecimal (base 16) | 7C89 |
| Base 3 | 1121201210 |
| As time | 31881 seconds = 8 h 51 min 21 s |
Is 31881 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 | Yes (31881 ÷ 3 = 10627) | 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 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31881 a prime number?
No. 31881 = 3 × 10627, so it is divisible by 3.
What are the factors of 31881?
1, 3, 10627, 31881.
What is 31881 in binary?
111110010001001 (hexadecimal 7C89, octal 76211).
What is the square root of 31881?
About 178.5525.
Is 31881 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 31881?
31881 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10627, the product of two primes.