The number 5721
5721 is a composite number with 4 divisors. Its prime factorisation is 3 × 1907. Divisors (4): 1, 3, 1907, 5721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 5721: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 1907, the product of two primes.
- 2
5721 is composite. Its prime factorisation is
- 3
The divisors add up to 7632; without 5721 itself that is 1911, so 5721 is deficient (1911 is less than 5721). Euler's totient φ(5721) = 3812 numbers up to 5721 share no factor with it.
- 4
The digits of 5721 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 80 steps to reach 1.
LaTeX source of the formulas on this page
\[ 5721 = 3 \times 1907 \]
5721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 7632 |
| Euler totient φ(n) | 3812 |
| Square | 32729841 |
| Cube | 187247420361 |
| Square root | 75.637292 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 80 |
| Scientific notation | 5.721 × |
5721 in other forms
| Form | Value |
|---|---|
| In words | five thousand seven hundred and twenty-one |
| Binary (base 2) | 1011001011001 |
| Octal (base 8) | 13131 |
| Hexadecimal (base 16) | 1659 |
| Base 3 | 21211220 |
| As time | 5721 seconds = 1 h 35 min 21 s |
Is 5721 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 (5721 ÷ 3 = 1907) | 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 2) | 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 1) | 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 5721 a prime number?
No. 5721 = 3 × 1907, so it is divisible by 3.
What are the factors of 5721?
1, 3, 1907, 5721.
What is 5721 in binary?
1011001011001 (hexadecimal 1659, octal 13131).
What is the square root of 5721?
About 75.6373.
Is 5721 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 5721?
5721 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 1907, the product of two primes.