The number 31921
31921 is a composite number with 4 divisors. Its prime factorisation is 137 × 233. Divisors (4): 1, 137, 233, 31921.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31921: a semiprime: 137 × 233, the product of two primes.
- 2
31921 is composite. Its prime factorisation is
- 3
The divisors add up to 32292; without 31921 itself that is 371, so 31921 is deficient (371 is less than 31921). Euler's totient φ(31921) = 31552 numbers up to 31921 share no factor with it.
- 4
The digits of 31921 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 98 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31921 = 137 \times 233 \]
31921 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 32292 |
| Euler totient φ(n) | 31552 |
| Square | 1018950241 |
| Cube | 32525910642961 |
| Square root | 178.664490 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 98 |
| Scientific notation | 3.1921 × |
31921 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand nine hundred and twenty-one |
| Binary (base 2) | 111110010110001 |
| Octal (base 8) | 76261 |
| Hexadecimal (base 16) | 7CB1 |
| Base 3 | 1121210021 |
| As time | 31921 seconds = 8 h 52 min 1 s |
Is 31921 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 | No (remainder 1) | 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 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 10) | 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 31921 a prime number?
No. 31921 = 137 × 233, so it is divisible by 137.
What are the factors of 31921?
1, 137, 233, 31921.
What is 31921 in binary?
111110010110001 (hexadecimal 7CB1, octal 76261).
What is the square root of 31921?
About 178.6645.
Is 31921 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 31921?
31921 is a semiprime: 137 × 233, the product of two primes.