The number 31281
31281 is a composite number with 4 divisors. Its prime factorisation is 3 × 10427. Divisors (4): 1, 3, 10427, 31281.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31281: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10427, the product of two primes.
- 2
31281 is composite. Its prime factorisation is
- 3
The divisors add up to 41712; without 31281 itself that is 10431, so 31281 is deficient (10431 is less than 31281). Euler's totient φ(31281) = 20852 numbers up to 31281 share no factor with it.
- 4
The digits of 31281 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 108 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31281 = 3 \times 10427 \]
31281 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 41712 |
| Euler totient φ(n) | 20852 |
| Square | 978500961 |
| Cube | 30608488561041 |
| Square root | 176.864355 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 108 |
| Scientific notation | 3.1281 × |
31281 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand two hundred and eighty-one |
| Binary (base 2) | 111101000110001 |
| Octal (base 8) | 75061 |
| Hexadecimal (base 16) | 7A31 |
| Base 3 | 1120220120 |
| As time | 31281 seconds = 8 h 41 min 21 s |
Is 31281 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 (31281 ÷ 3 = 10427) | 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 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | 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 8) | 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 31281 a prime number?
No. 31281 = 3 × 10427, so it is divisible by 3.
What are the factors of 31281?
1, 3, 10427, 31281.
What is 31281 in binary?
111101000110001 (hexadecimal 7A31, octal 75061).
What is the square root of 31281?
About 176.8644.
Is 31281 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 31281?
31281 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 10427, the product of two primes.