The number 21382
21382 is a composite number with 4 divisors. Its prime factorisation is 2 × 10691. Divisors (4): 1, 2, 10691, 21382.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21382: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 10691, the product of two primes.
- 2
21382 is composite. Its prime factorisation is
- 3
The divisors add up to 32076; without 21382 itself that is 10694, so 21382 is deficient (10694 is less than 21382). Euler's totient φ(21382) = 10690 numbers up to 21382 share no factor with it.
- 4
The digits of 21382 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 162 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21382 = 2 \times 10691 \]
21382 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 32076 |
| Euler totient φ(n) | 10690 |
| Square | 457189924 |
| Cube | 9775634954968 |
| Square root | 146.225853 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.1382 × |
21382 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand three hundred and eighty-two |
| Binary (base 2) | 101001110000110 |
| Octal (base 8) | 51606 |
| Hexadecimal (base 16) | 5386 |
| Base 3 | 1002022221 |
| As time | 21382 seconds = 5 h 56 min 22 s |
Is 21382 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21382 ÷ 2 = 10691) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | 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 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 2) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 10) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21382 a prime number?
No. 21382 = 2 × 10691, so it is divisible by 2.
What are the factors of 21382?
1, 2, 10691, 21382.
What is 21382 in binary?
101001110000110 (hexadecimal 5386, octal 51606).
What is the square root of 21382?
About 146.2259.
Is 21382 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21382?
21382 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 2 × 10691, the product of two primes.