The number 21031
21031 is the 2367th prime number. Its only divisors are 1 and 21031.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21031: the 2367th prime number.
- 2
21031 is prime, so its only factors are 1 and 21031. It is the 2367th prime; the next prime is 21059 and the one before is 21023.
- 3
The divisors add up to 21032; without 21031 itself that is 1, so 21031 is deficient (1 is less than 21031). Euler's totient φ(21031) = 21030 numbers up to 21031 share no factor with it.
- 4
The digits of 21031 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 87 steps to reach 1.
21031 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 21032 |
| Euler totient φ(n) | 21030 |
| Square | 442302961 |
| Cube | 9302073572791 |
| Square root | 145.020688 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 87 |
| Scientific notation | 2.1031 × |
21031 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and thirty-one |
| Binary (base 2) | 101001000100111 |
| Octal (base 8) | 51047 |
| Hexadecimal (base 16) | 5227 |
| Base 3 | 1001211221 |
| As time | 21031 seconds = 5 h 50 min 31 s |
Is 21031 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 3) | 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 7) | 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 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21031 a prime number?
Yes. 21031 is divisible only by 1 and itself.
What are the factors of 21031?
1, 21031.
What is 21031 in binary?
101001000100111 (hexadecimal 5227, octal 51047).
What is the square root of 21031?
About 145.0207.
Is 21031 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 21031?
21031 is the 2367th prime number.