The number 6821
6821 is a composite number with 4 divisors. Its prime factorisation is 19 × 359. Divisors (4): 1, 19, 359, 6821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 6821: a semiprime: 19 × 359, the product of two primes.
- 2
6821 is composite. Its prime factorisation is
- 3
The divisors add up to 7200; without 6821 itself that is 379, so 6821 is deficient (379 is less than 6821). Euler's totient φ(6821) = 6444 numbers up to 6821 share no factor with it.
- 4
The digits of 6821 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 137 steps to reach 1.
LaTeX source of the formulas on this page
\[ 6821 = 19 \times 359 \]
6821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 7200 |
| Euler totient φ(n) | 6444 |
| Square | 46526041 |
| Cube | 317354125661 |
| Square root | 82.589346 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 137 |
| Scientific notation | 6.821 × |
6821 in other forms
| Form | Value |
|---|---|
| In words | six thousand eight hundred and twenty-one |
| Binary (base 2) | 1101010100101 |
| Octal (base 8) | 15245 |
| Hexadecimal (base 16) | 1AA5 |
| Base 3 | 100100122 |
| As time | 6821 seconds = 1 h 53 min 41 s |
Is 6821 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 2) | 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 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 8) | 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 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 6821 a prime number?
No. 6821 = 19 × 359, so it is divisible by 19.
What are the factors of 6821?
1, 19, 359, 6821.
What is 6821 in binary?
1101010100101 (hexadecimal 1AA5, octal 15245).
What is the square root of 6821?
About 82.5893.
Is 6821 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 6821?
6821 is a semiprime: 19 × 359, the product of two primes.