The number 21231
21231 is a composite number with 12 divisors. Its prime factorisation is × 7 × 337. Divisors (12): 1, 3, 7, 9, 21, 63, 337, 1011, 2359, 3033, 7077, 21231.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21231: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.
- 2
21231 is composite. Its prime factorisation is
- 3
The divisors add up to 35152; without 21231 itself that is 13921, so 21231 is deficient (13921 is less than 21231). Euler's totient φ(21231) = 12096 numbers up to 21231 share no factor with it.
- 4
The digits of 21231 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21231 = 3^{2} \times 7 \times 337 \]21231 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 35152 |
| Euler totient φ(n) | 12096 |
| Square | 450755361 |
| Cube | 9569987069391 |
| Square root | 145.708613 (= 3√2359) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1231 × |
21231 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and thirty-one |
| Binary (base 2) | 101001011101111 |
| Octal (base 8) | 51357 |
| Hexadecimal (base 16) | 52EF |
| Base 3 | 1002010100 |
| As time | 21231 seconds = 5 h 53 min 51 s |
Is 21231 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 | Yes (21231 ÷ 3 = 7077) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21231 ÷ 7 = 3033) | 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 | Yes (21231 ÷ 9 = 2359) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21231 a prime number?
No. 21231 = × 7 × 337, so it is divisible by 3.
What are the factors of 21231?
1, 3, 7, 9, 21, 63, 337, 1011, 2359, 3033, 7077, 21231.
What is 21231 in binary?
101001011101111 (hexadecimal 52EF, octal 51357).
What is the square root of 21231?
About 145.7086, exactly 3√2359.
Is 21231 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 21231?
21231 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.