The number 21742
21742 is a composite number with 8 divisors. Its prime factorisation is 2 × 7 × 1553. Divisors (8): 1, 2, 7, 14, 1553, 3106, 10871, 21742.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21742 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21742 is composite. Its prime factorisation is
- 3
The divisors add up to 37296; without 21742 itself that is 15554, so 21742 is deficient (15554 is less than 21742). Euler's totient φ(21742) = 9312 numbers up to 21742 share no factor with it.
- 4
The digits of 21742 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 118 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21742 = 2 \times 7 \times 1553 \]
21742 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 37296 |
| Euler totient φ(n) | 9312 |
| Square | 472714564 |
| Cube | 10277760050488 |
| Square root | 147.451687 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 118 |
| Scientific notation | 2.1742 × |
21742 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand seven hundred and forty-two |
| Binary (base 2) | 101010011101110 |
| Octal (base 8) | 52356 |
| Hexadecimal (base 16) | 54EE |
| Base 3 | 1002211021 |
| As time | 21742 seconds = 6 h 2 min 22 s |
Is 21742 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21742 ÷ 2 = 10871) | 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 | Yes (21742 ÷ 7 = 3106) | 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 6) | 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 21742 a prime number?
No. 21742 = 2 × 7 × 1553, so it is divisible by 2.
What are the factors of 21742?
1, 2, 7, 14, 1553, 3106, 10871, 21742.
What is 21742 in binary?
101010011101110 (hexadecimal 54EE, octal 52356).
What is the square root of 21742?
About 147.4517.
Is 21742 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21742?
It is a composite number with 8 divisors.