The number 18521
18521 is a twin prime (18521 and 18523 are both prime) and the 2121st prime number. Its only divisors are 1 and 18521.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 18521: a twin prime (18521 and 18523 are both prime); the 2121st prime number.
- 2
18521 is prime, so its only factors are 1 and 18521. It is the 2121st prime; the next prime is 18523 and the one before is 18517.
- 3
The divisors add up to 18522; without 18521 itself that is 1, so 18521 is deficient (1 is less than 18521). Euler's totient φ(18521) = 18520 numbers up to 18521 share no factor with it.
- 4
The digits of 18521 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 48 steps to reach 1.
18521 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 18522 |
| Euler totient φ(n) | 18520 |
| Square | 343027441 |
| Cube | 6353211234761 |
| Square root | 136.091881 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 48 |
| Scientific notation | 1.8521 × |
18521 in other forms
| Form | Value |
|---|---|
| In words | eighteen thousand five hundred and twenty-one |
| Binary (base 2) | 100100001011001 |
| Octal (base 8) | 44131 |
| Hexadecimal (base 16) | 4859 |
| Base 3 | 221101222 |
| As time | 18521 seconds = 5 h 8 min 41 s |
Is 18521 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 6) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | 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 8) | 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 18521 a prime number?
Yes. 18521 is divisible only by 1 and itself.
What are the factors of 18521?
1, 18521.
What is 18521 in binary?
100100001011001 (hexadecimal 4859, octal 44131).
What is the square root of 18521?
About 136.0919.
Is 18521 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 18521?
18521 is a twin prime (18521 and 18523 are both prime); the 2121st prime number.