The number 21542
21542 is a composite number with 4 divisors. Its prime factorisation is 2 × 10771. Divisors (4): 1, 2, 10771, 21542.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21542: a semiprime: 2 × 10771, the product of two primes.
- 2
21542 is composite. Its prime factorisation is
- 3
The divisors add up to 32316; without 21542 itself that is 10774, so 21542 is deficient (10774 is less than 21542). Euler's totient φ(21542) = 10770 numbers up to 21542 share no factor with it.
- 4
The digits of 21542 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21542 = 2 \times 10771 \]
21542 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 32316 |
| Euler totient φ(n) | 10770 |
| Square | 464057764 |
| Cube | 9996732352088 |
| Square root | 146.771932 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1542 × |
21542 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred and forty-two |
| Binary (base 2) | 101010000100110 |
| Octal (base 8) | 52046 |
| Hexadecimal (base 16) | 5426 |
| Base 3 | 1002112212 |
| As time | 21542 seconds = 5 h 59 min 2 s |
Is 21542 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21542 ÷ 2 = 10771) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | 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 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 5) | 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 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21542 a prime number?
No. 21542 = 2 × 10771, so it is divisible by 2.
What are the factors of 21542?
1, 2, 10771, 21542.
What is 21542 in binary?
101010000100110 (hexadecimal 5426, octal 52046).
What is the square root of 21542?
About 146.7719.
Is 21542 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 21542?
21542 is a semiprime: 2 × 10771, the product of two primes.