The number 6721
6721 is a composite number with 8 divisors. Its prime factorisation is 11 × 13 × 47. Divisors (8): 1, 11, 13, 47, 143, 517, 611, 6721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
6721 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
6721 is composite. Its prime factorisation is
- 3
The divisors add up to 8064; without 6721 itself that is 1343, so 6721 is deficient (1343 is less than 6721). Euler's totient φ(6721) = 5520 numbers up to 6721 share no factor with it.
- 4
The digits of 6721 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 44 steps to reach 1.
LaTeX source of the formulas on this page
\[ 6721 = 11 \times 13 \times 47 \]
6721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 8064 |
| Euler totient φ(n) | 5520 |
| Square | 45171841 |
| Cube | 303599943361 |
| Square root | 81.981705 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 44 |
| Scientific notation | 6.721 × |
6721 in other forms
| Form | Value |
|---|---|
| In words | six thousand seven hundred and twenty-one |
| Binary (base 2) | 1101001000001 |
| Octal (base 8) | 15101 |
| Hexadecimal (base 16) | 1A41 |
| Base 3 | 100012221 |
| As time | 6721 seconds = 1 h 52 min 1 s |
Is 6721 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 | Yes (6721 ÷ 11 = 611) | 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 6721 a prime number?
No. 6721 = 11 × 13 × 47, so it is divisible by 11.
What are the factors of 6721?
1, 11, 13, 47, 143, 517, 611, 6721.
What is 6721 in binary?
1101001000001 (hexadecimal 1A41, octal 15101).
What is the square root of 6721?
About 81.9817.
Is 6721 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 6721?
It is a composite number with 8 divisors.