The number 30721
30721 is a composite number with 4 divisors. Its prime factorisation is 31 × 991. Divisors (4): 1, 31, 991, 30721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 30721: a semiprime: 31 × 991, the product of two primes.
- 2
30721 is composite. Its prime factorisation is
- 3
The divisors add up to 31744; without 30721 itself that is 1023, so 30721 is deficient (1023 is less than 30721). Euler's totient φ(30721) = 29700 numbers up to 30721 share no factor with it.
- 4
The digits of 30721 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 178 steps to reach 1.
LaTeX source of the formulas on this page
\[ 30721 = 31 \times 991 \]
30721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 31744 |
| Euler totient φ(n) | 29700 |
| Square | 943779841 |
| Cube | 28993860495361 |
| Square root | 175.274071 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 178 |
| Scientific notation | 3.0721 × |
30721 in other forms
| Form | Value |
|---|---|
| In words | thirty thousand seven hundred and twenty-one |
| Binary (base 2) | 111100000000001 |
| Octal (base 8) | 74001 |
| Hexadecimal (base 16) | 7801 |
| Base 3 | 1120010211 |
| As time | 30721 seconds = 8 h 32 min 1 s |
Is 30721 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 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 4) | 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 30721 a prime number?
No. 30721 = 31 × 991, so it is divisible by 31.
What are the factors of 30721?
1, 31, 991, 30721.
What is 30721 in binary?
111100000000001 (hexadecimal 7801, octal 74001).
What is the square root of 30721?
About 175.2741.
Is 30721 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 30721?
30721 is a semiprime: 31 × 991, the product of two primes.