The number 21187
21187 is the 2382nd prime number. Its only divisors are 1 and 21187.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21187: the 2382nd prime number.
- 2
21187 is prime, so its only factors are 1 and 21187. It is the 2382nd prime; the next prime is 21191 and the one before is 21179.
- 3
The divisors add up to 21188; without 21187 itself that is 1, so 21187 is deficient (1 is less than 21187). Euler's totient φ(21187) = 21186 numbers up to 21187 share no factor with it.
- 4
The digits of 21187 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 131 steps to reach 1.
21187 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21188 |
| Euler totient φ(n) | 21186 |
| Square | 448888969 |
| Cube | 9510610586203 |
| Square root | 145.557549 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 131 |
| Scientific notation | 2.1187 × |
21187 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and eighty-seven |
| Binary (base 2) | 101001011000011 |
| Octal (base 8) | 51303 |
| Hexadecimal (base 16) | 52C3 |
| Base 3 | 1002001201 |
| As time | 21187 seconds = 5 h 53 min 7 s |
Is 21187 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 2) | 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 3) | 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 7) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21187 a prime number?
Yes. 21187 is divisible only by 1 and itself.
What are the factors of 21187?
1, 21187.
What is 21187 in binary?
101001011000011 (hexadecimal 52C3, octal 51303).
What is the square root of 21187?
About 145.5575.
Is 21187 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 21187?
21187 is the 2382nd prime number.