The number 39821
39821 is the 4184th prime number. Its only divisors are 1 and 39821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 39821: the 4184th prime number.
- 2
39821 is prime, so its only factors are 1 and 39821. It is the 4184th prime; the next prime is 39827 and the one before is 39799.
- 3
The divisors add up to 39822; without 39821 itself that is 1, so 39821 is deficient (1 is less than 39821). Euler's totient φ(39821) = 39820 numbers up to 39821 share no factor with it.
- 4
The digits of 39821 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 93 steps to reach 1.
39821 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 39822 |
| Euler totient φ(n) | 39820 |
| Square | 1585712041 |
| Cube | 63144639184661 |
| Square root | 199.551998 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 93 |
| Scientific notation | 3.9821 × |
39821 in other forms
| Form | Value |
|---|---|
| In words | thirty-nine thousand eight hundred and twenty-one |
| Binary (base 2) | 1001101110001101 |
| Octal (base 8) | 115615 |
| Hexadecimal (base 16) | 9B8D |
| Base 3 | 2000121212 |
| As time | 39821 seconds = 11 h 3 min 41 s |
Is 39821 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 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 5) | 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 39821 a prime number?
Yes. 39821 is divisible only by 1 and itself.
What are the factors of 39821?
1, 39821.
What is 39821 in binary?
1001101110001101 (hexadecimal 9B8D, octal 115615).
What is the square root of 39821?
About 199.5520.
Is 39821 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 39821?
39821 is the 4184th prime number.