The number 20005
20005 is a composite number with 4 divisors. Its prime factorisation is 5 × 4001. Divisors (4): 1, 5, 4001, 20005.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 20005: a semiprime: 5 × 4001, the product of two primes.
- 2
20005 is composite. Its prime factorisation is
- 3
The divisors add up to 24012; without 20005 itself that is 4007, so 20005 is deficient (4007 is less than 20005). Euler's totient φ(20005) = 16000 numbers up to 20005 share no factor with it.
- 4
The digits of 20005 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 66 steps to reach 1.
LaTeX source of the formulas on this page
\[ 20005 = 5 \times 4001 \]
20005 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 24012 |
| Euler totient φ(n) | 16000 |
| Square | 400200025 |
| Cube | 8006001500125 |
| Square root | 141.439033 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 66 |
| Scientific notation | 2.0005 × |
20005 in other forms
| Form | Value |
|---|---|
| In words | twenty thousand and five |
| Binary (base 2) | 100111000100101 |
| Octal (base 8) | 47045 |
| Hexadecimal (base 16) | 4E25 |
| Base 3 | 1000102221 |
| As time | 20005 seconds = 5 h 33 min 25 s |
Is 20005 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (20005 ÷ 5 = 4001) | 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 5) | 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 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 20005 a prime number?
No. 20005 = 5 × 4001, so it is divisible by 5.
What are the factors of 20005?
1, 5, 4001, 20005.
What is 20005 in binary?
100111000100101 (hexadecimal 4E25, octal 47045).
What is the square root of 20005?
About 141.4390.
Is 20005 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 20005?
20005 is a semiprime: 5 × 4001, the product of two primes.