The number 21982
21982 is a composite number with 8 divisors. Its prime factorisation is 2 × 29 × 379. Divisors (8): 1, 2, 29, 58, 379, 758, 10991, 21982.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21982 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21982 is composite. Its prime factorisation is
- 3
The divisors add up to 34200; without 21982 itself that is 12218, so 21982 is deficient (12218 is less than 21982). Euler's totient φ(21982) = 10584 numbers up to 21982 share no factor with it.
- 4
The digits of 21982 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21982 = 2 \times 29 \times 379 \]
21982 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 34200 |
| Euler totient φ(n) | 10584 |
| Square | 483208324 |
| Cube | 10621885378168 |
| Square root | 148.263279 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1982 × |
21982 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and eighty-two |
| Binary (base 2) | 101010111011110 |
| Octal (base 8) | 52736 |
| Hexadecimal (base 16) | 55DE |
| Base 3 | 1010011011 |
| As time | 21982 seconds = 6 h 6 min 22 s |
Is 21982 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21982 ÷ 2 = 10991) | 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 2) | 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 4) | 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 4) | 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 21982 a prime number?
No. 21982 = 2 × 29 × 379, so it is divisible by 2.
What are the factors of 21982?
1, 2, 29, 58, 379, 758, 10991, 21982.
What is 21982 in binary?
101010111011110 (hexadecimal 55DE, octal 52736).
What is the square root of 21982?
About 148.2633.
Is 21982 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 21982?
It is a composite number with 8 divisors.