The number 20521
20521 is the 2316th prime number. Its only divisors are 1 and 20521.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20521: the 2316th prime number.
- 2
20521 is prime, so its only factors are 1 and 20521. It is the 2316th prime; the next prime is 20533 and the one before is 20509.
- 3
The divisors add up to 20522; without 20521 itself that is 1, so 20521 is deficient (1 is less than 20521). Euler's totient φ(20521) = 20520 numbers up to 20521 share no factor with it.
- 4
The digits of 20521 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 180 steps to reach 1.
20521 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 20522 |
| Euler totient φ(n) | 20520 |
| Square | 421111441 |
| Cube | 8641627880761 |
| Square root | 143.251527 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 180 |
| Scientific notation | 2.0521 × |
20521 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand five hundred and twenty-one |
| Binary (base 2) | 101000000101001 |
| Octal (base 8) | 50051 |
| Hexadecimal (base 16) | 5029 |
| Base 3 | 1001011001 |
| As time | 20521 seconds = 5 h 42 min 1 s |
Is 20521 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 4) | 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 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 6) | 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 20521 a prime number?
Yes. 20521 is divisible only by 1 and itself.
What are the factors of 20521?
1, 20521.
What is 20521 in binary?
101000000101001 (hexadecimal 5029, octal 50051).
What is the square root of 20521?
About 143.2515.
Is 20521 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 20521?
20521 is the 2316th prime number.