The number 13821
13821 is a composite number with 8 divisors. Its prime factorisation is 3 × 17 × 271. Divisors (8): 1, 3, 17, 51, 271, 813, 4607, 13821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 13821: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
13821 is composite. Its prime factorisation is
- 3
The divisors add up to 19584; without 13821 itself that is 5763, so 13821 is deficient (5763 is less than 13821). Euler's totient φ(13821) = 8640 numbers up to 13821 share no factor with it.
- 4
The digits of 13821 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 58 steps to reach 1.
LaTeX source of the formulas on this page
\[ 13821 = 3 \times 17 \times 271 \]
13821 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 19584 |
| Euler totient φ(n) | 8640 |
| Square | 191020041 |
| Cube | 2640087986661 |
| Square root | 117.562749 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 58 |
| Scientific notation | 1.3821 × |
13821 in other forms
| Form | Value |
|---|---|
| In words | thirteen thousand eight hundred and twenty-one |
| Binary (base 2) | 11010111111101 |
| Octal (base 8) | 32775 |
| Hexadecimal (base 16) | 35FD |
| Base 3 | 200221220 |
| As time | 13821 seconds = 3 h 50 min 21 s |
Is 13821 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 (13821 ÷ 3 = 4607) | 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 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 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 5) | 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 13821 a prime number?
No. 13821 = 3 × 17 × 271, so it is divisible by 3.
What are the factors of 13821?
1, 3, 17, 51, 271, 813, 4607, 13821.
What is 13821 in binary?
11010111111101 (hexadecimal 35FD, octal 32775).
What is the square root of 13821?
About 117.5627.
Is 13821 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 13821?
13821 is a happy number: repeatedly adding the squares of its digits reaches 1.