The number 21942
21942 is a composite number with 24 divisors. Its prime factorisation is 2 × × 23 × 53. Divisors (24): 1, 2, 3, 6, 9, 18, 23, 46, 53, 69, 106, 138, 159, 207, 318, 414 … 21942.
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How to work it out
- 1
What is special about 21942: a Harshad number: divisible by its digit sum 18.
- 2
21942 is composite. Its prime factorisation is
- 3
The divisors add up to 50544; without 21942 itself that is 28602, so 21942 is abundant (28602 is more than 21942). Euler's totient φ(21942) = 6864 numbers up to 21942 share no factor with it.
- 4
The digits of 21942 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 268 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21942 = 2 \times 3^{2} \times 23 \times 53 \]21942 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 50544 |
| Euler totient φ(n) | 6864 |
| Square | 481451364 |
| Cube | 10564005828888 |
| Square root | 148.128323 (= 3√2438) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 268 |
| Scientific notation | 2.1942 × |
21942 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and forty-two |
| Binary (base 2) | 101010110110110 |
| Octal (base 8) | 52666 |
| Hexadecimal (base 16) | 55B6 |
| Base 3 | 1010002200 |
| As time | 21942 seconds = 6 h 5 min 42 s |
Is 21942 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21942 ÷ 2 = 10971) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21942 ÷ 3 = 7314) | 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 | Yes (21942 ÷ 6 = 3657) | 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 (21942 ÷ 9 = 2438) | 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 8) | 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 21942 a prime number?
No. 21942 = 2 × × 23 × 53, so it is divisible by 2.
What are the factors of 21942?
1, 2, 3, 6, 9, 18, 23, 46, 53, 69, 106, 138, 159, 207, 318, 414, 477, 954, 1219, 2438, 3657, 7314, 10971, 21942.
What is 21942 in binary?
101010110110110 (hexadecimal 55B6, octal 52666).
What is the square root of 21942?
About 148.1283, exactly 3√2438.
Is 21942 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21942?
21942 is a Harshad number: divisible by its digit sum 18.