The number 21221
21221 is the 2386th prime number. Its only divisors are 1 and 21221.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21221: the 2386th prime number.
- 2
21221 is prime, so its only factors are 1 and 21221. It is the 2386th prime; the next prime is 21227 and the one before is 21211.
- 3
The divisors add up to 21222; without 21221 itself that is 1, so 21221 is deficient (1 is less than 21221). Euler's totient φ(21221) = 21220 numbers up to 21221 share no factor with it.
- 4
The digits of 21221 add up to 8, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
21221 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21222 |
| Euler totient φ(n) | 21220 |
| Square | 450330841 |
| Cube | 9556470776861 |
| Square root | 145.674294 |
| Digit sum / digital root | 8 / 8 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1221 × |
21221 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and twenty-one |
| Binary (base 2) | 101001011100101 |
| Octal (base 8) | 51345 |
| Hexadecimal (base 16) | 52E5 |
| Base 3 | 1002002222 |
| As time | 21221 seconds = 5 h 53 min 41 s |
Is 21221 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 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 5) | 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 2) | 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 21221 a prime number?
Yes. 21221 is divisible only by 1 and itself.
What are the factors of 21221?
1, 21221.
What is 21221 in binary?
101001011100101 (hexadecimal 52E5, octal 51345).
What is the square root of 21221?
About 145.6743.
Is 21221 divisible by 3?
No. Its digits add up to 8, which is not a multiple of 3.
What is special about the number 21221?
21221 is the 2386th prime number.