The number 11821
11821 is the 1417th prime number. Its only divisors are 1 and 11821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 11821: the 1417th prime number.
- 2
11821 is prime, so its only factors are 1 and 11821. It is the 1417th prime; the next prime is 11827 and the one before is 11813.
- 3
The divisors add up to 11822; without 11821 itself that is 1, so 11821 is deficient (1 is less than 11821). Euler's totient φ(11821) = 11820 numbers up to 11821 share no factor with it.
- 4
The digits of 11821 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 143 steps to reach 1.
11821 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 11822 |
| Euler totient φ(n) | 11820 |
| Square | 139736041 |
| Cube | 1651819740661 |
| Square root | 108.724422 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 143 |
| Scientific notation | 1.1821 × |
11821 in other forms
| Form | Value |
|---|---|
| In words | eleven thousand eight hundred and twenty-one |
| Binary (base 2) | 10111000101101 |
| Octal (base 8) | 27055 |
| Hexadecimal (base 16) | 2E2D |
| Base 3 | 121012211 |
| As time | 11821 seconds = 3 h 17 min 1 s |
Is 11821 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 5) | 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 7) | 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 11821 a prime number?
Yes. 11821 is divisible only by 1 and itself.
What are the factors of 11821?
1, 11821.
What is 11821 in binary?
10111000101101 (hexadecimal 2E2D, octal 27055).
What is the square root of 11821?
About 108.7244.
Is 11821 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 11821?
11821 is the 1417th prime number.