The number 31381
31381 is a composite number with 4 divisors. Its prime factorisation is 7 × 4483. Divisors (4): 1, 7, 4483, 31381.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31381: a semiprime: 7 × 4483, the product of two primes.
- 2
31381 is composite. Its prime factorisation is
- 3
The divisors add up to 35872; without 31381 itself that is 4491, so 31381 is deficient (4491 is less than 31381). Euler's totient φ(31381) = 26892 numbers up to 31381 share no factor with it.
- 4
The digits of 31381 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 178 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31381 = 7 \times 4483 \]
31381 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 35872 |
| Euler totient φ(n) | 26892 |
| Square | 984767161 |
| Cube | 30902978279341 |
| Square root | 177.146832 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 178 |
| Scientific notation | 3.1381 × |
31381 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand three hundred and eighty-one |
| Binary (base 2) | 111101010010101 |
| Octal (base 8) | 75225 |
| Hexadecimal (base 16) | 7A95 |
| Base 3 | 1121001021 |
| As time | 31381 seconds = 8 h 43 min 1 s |
Is 31381 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 1) | 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 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (31381 ÷ 7 = 4483) | 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 7) | 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 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31381 a prime number?
No. 31381 = 7 × 4483, so it is divisible by 7.
What are the factors of 31381?
1, 7, 4483, 31381.
What is 31381 in binary?
111101010010101 (hexadecimal 7A95, octal 75225).
What is the square root of 31381?
About 177.1468.
Is 31381 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 31381?
31381 is a semiprime: 7 × 4483, the product of two primes.