The number 4021
4021 is a twin prime (4019 and 4021 are both prime) and the 556th prime number. Its only divisors are 1 and 4021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 4021: a twin prime (4019 and 4021 are both prime); the 556th prime number.
- 2
4021 is prime, so its only factors are 1 and 4021. It is the 556th prime; the next prime is 4027 and the one before is 4019.
- 3
The divisors add up to 4022; without 4021 itself that is 1, so 4021 is deficient (1 is less than 4021). Euler's totient φ(4021) = 4020 numbers up to 4021 share no factor with it.
- 4
The digits of 4021 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 69 steps to reach 1.
4021 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 4022 |
| Euler totient φ(n) | 4020 |
| Square | 16168441 |
| Cube | 65013301261 |
| Square root | 63.411355 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 69 |
| Scientific notation | 4.021 × |
4021 in other forms
| Form | Value |
|---|---|
| In words | four thousand and twenty-one |
| Binary (base 2) | 111110110101 |
| Octal (base 8) | 7665 |
| Hexadecimal (base 16) | FB5 |
| Base 3 | 12111221 |
| As time | 4021 seconds = 1 h 7 min 1 s |
Is 4021 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 3) | 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 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 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 4021 a prime number?
Yes. 4021 is divisible only by 1 and itself.
What are the factors of 4021?
1, 4021.
What is 4021 in binary?
111110110101 (hexadecimal FB5, octal 7665).
What is the square root of 4021?
About 63.4114.
Is 4021 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 4021?
4021 is a twin prime (4019 and 4021 are both prime); the 556th prime number.