The number 21643
21643 is a composite number with 4 divisors. Its prime factorisation is 23 × 941. Divisors (4): 1, 23, 941, 21643.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21643: a semiprime: 23 × 941, the product of two primes.
- 2
21643 is composite. Its prime factorisation is
- 3
The divisors add up to 22608; without 21643 itself that is 965, so 21643 is deficient (965 is less than 21643). Euler's totient φ(21643) = 20680 numbers up to 21643 share no factor with it.
- 4
The digits of 21643 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
\[ 21643 = 23 \times 941 \]
21643 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 22608 |
| Euler totient φ(n) | 20680 |
| Square | 468419449 |
| Cube | 10138002134707 |
| Square root | 147.115601 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.1643 × |
21643 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand six hundred and forty-three |
| Binary (base 2) | 101010010001011 |
| Octal (base 8) | 52213 |
| Hexadecimal (base 16) | 548B |
| Base 3 | 1002200121 |
| As time | 21643 seconds = 6 h 0 min 43 s |
Is 21643 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 3) | 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 3) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21643 a prime number?
No. 21643 = 23 × 941, so it is divisible by 23.
What are the factors of 21643?
1, 23, 941, 21643.
What is 21643 in binary?
101010010001011 (hexadecimal 548B, octal 52213).
What is the square root of 21643?
About 147.1156.
Is 21643 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 21643?
21643 is a semiprime: 23 × 941, the product of two primes.