The number 20021
20021 is a twin prime (20021 and 20023 are both prime) and the 2264th prime number. Its only divisors are 1 and 20021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20021: a twin prime (20021 and 20023 are both prime); the 2264th prime number.
- 2
20021 is prime, so its only factors are 1 and 20021. It is the 2264th prime; the next prime is 20023 and the one before is 20011.
- 3
The divisors add up to 20022; without 20021 itself that is 1, so 20021 is deficient (1 is less than 20021). Euler's totient φ(20021) = 20020 numbers up to 20021 share no factor with it.
- 4
The digits of 20021 add up to 5, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 30 steps to reach 1.
20021 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 20022 |
| Euler totient φ(n) | 20020 |
| Square | 400840441 |
| Cube | 8025226469261 |
| Square root | 141.495583 |
| Digit sum / digital root | 5 / 5 |
| Collatz steps to 1 | 30 |
| Scientific notation | 2.0021 × |
20021 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand and twenty-one |
| Binary (base 2) | 100111000110101 |
| Octal (base 8) | 47065 |
| Hexadecimal (base 16) | 4E35 |
| Base 3 | 1000110112 |
| As time | 20021 seconds = 5 h 33 min 41 s |
Is 20021 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 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 5) | 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 1) | 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 20021 a prime number?
Yes. 20021 is divisible only by 1 and itself.
What are the factors of 20021?
1, 20021.
What is 20021 in binary?
100111000110101 (hexadecimal 4E35, octal 47065).
What is the square root of 20021?
About 141.4956.
Is 20021 divisible by 3?
No. Its digits add up to 5, which is not a multiple of 3.
What is special about the number 20021?
20021 is a twin prime (20021 and 20023 are both prime); the 2264th prime number.