The number 21438
21438 is a composite number with 16 divisors. Its prime factorisation is 2 × × 397. Divisors (16): 1, 2, 3, 6, 9, 18, 27, 54, 397, 794, 1191, 2382, 3573, 7146, 10719, 21438.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21438: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.
- 2
21438 is composite. Its prime factorisation is
- 3
The divisors add up to 47760; without 21438 itself that is 26322, so 21438 is abundant (26322 is more than 21438). Euler's totient φ(21438) = 7128 numbers up to 21438 share no factor with it.
- 4
The digits of 21438 add up to 18, 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
\[ 21438 = 2 \times 3^{3} \times 397 \]21438 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 47760 |
| Euler totient φ(n) | 7128 |
| Square | 459587844 |
| Cube | 9852644199672 |
| Square root | 146.417212 (= 3√2382) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1438 × |
21438 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand four hundred and thirty-eight |
| Binary (base 2) | 101001110111110 |
| Octal (base 8) | 51676 |
| Hexadecimal (base 16) | 53BE |
| Base 3 | 1002102000 |
| As time | 21438 seconds = 5 h 57 min 18 s |
Is 21438 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21438 ÷ 2 = 10719) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21438 ÷ 3 = 7146) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21438 ÷ 6 = 3573) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21438 ÷ 9 = 2382) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | 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 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21438 a prime number?
No. 21438 = 2 × × 397, so it is divisible by 2.
What are the factors of 21438?
1, 2, 3, 6, 9, 18, 27, 54, 397, 794, 1191, 2382, 3573, 7146, 10719, 21438.
What is 21438 in binary?
101001110111110 (hexadecimal 53BE, octal 51676).
What is the square root of 21438?
About 146.4172, exactly 3√2382.
Is 21438 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21438?
21438 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 18.