The number 71821
71821 is the 7108th prime number. Its only divisors are 1 and 71821.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 71821: the 7108th prime number.
- 2
71821 is prime, so its only factors are 1 and 71821. It is the 7108th prime; the next prime is 71837 and the one before is 71809.
- 3
The divisors add up to 71822; without 71821 itself that is 1, so 71821 is deficient (1 is less than 71821). Euler's totient φ(71821) = 71820 numbers up to 71821 share no factor with it.
- 4
The digits of 71821 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 50 steps to reach 1.
71821 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 71822 |
| Euler totient φ(n) | 71820 |
| Square | 5158256041 |
| Cube | 370471107120661 |
| Square root | 267.994403 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 50 |
| Scientific notation | 7.1821 × |
71821 in other forms
| Form | Value |
|---|---|
| In words | seventy-one thousand eight hundred and twenty-one |
| Binary (base 2) | 10001100010001101 |
| Octal (base 8) | 214215 |
| Hexadecimal (base 16) | 1188D |
| Base 3 | 10122112001 |
| As time | 71821 seconds = 19 h 57 min 1 s |
Is 71821 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | 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 2) | 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 71821 a prime number?
Yes. 71821 is divisible only by 1 and itself.
What are the factors of 71821?
1, 71821.
What is 71821 in binary?
10001100010001101 (hexadecimal 1188D, octal 214215).
What is the square root of 71821?
About 267.9944.
Is 71821 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 71821?
71821 is the 7108th prime number.