The number 9871
9871 is the 1218th prime number. Its only divisors are 1 and 9871.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 9871: the 1218th prime number.
- 2
9871 is prime, so its only factors are 1 and 9871. It is the 1218th prime; the next prime is 9883 and the one before is 9859.
- 3
The divisors add up to 9872; without 9871 itself that is 1, so 9871 is deficient (1 is less than 9871). Euler's totient φ(9871) = 9870 numbers up to 9871 share no factor with it.
- 4
The digits of 9871 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 197 steps to reach 1.
9871 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 9872 |
| Euler totient φ(n) | 9870 |
| Square | 97436641 |
| Cube | 961797083311 |
| Square root | 99.352906 |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 197 |
| Scientific notation | 9.871 × |
9871 in other forms
| Form | Value |
|---|---|
| In words | nine thousand eight hundred and seventy-one |
| Binary (base 2) | 10011010001111 |
| Octal (base 8) | 23217 |
| Hexadecimal (base 16) | 268F |
| Base 3 | 111112121 |
| As time | 9871 seconds = 2 h 44 min 31 s |
Is 9871 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 3) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 9871 a prime number?
Yes. 9871 is divisible only by 1 and itself.
What are the factors of 9871?
1, 9871.
What is 9871 in binary?
10011010001111 (hexadecimal 268F, octal 23217).
What is the square root of 9871?
About 99.3529.
Is 9871 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 9871?
9871 is the 1218th prime number.