The number 18021
18021 is a composite number with 4 divisors. Its prime factorisation is 3 × 6007. Divisors (4): 1, 3, 6007, 18021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 18021: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 6007, the product of two primes.
- 2
18021 is composite. Its prime factorisation is
- 3
The divisors add up to 24032; without 18021 itself that is 6011, so 18021 is deficient (6011 is less than 18021). Euler's totient φ(18021) = 12012 numbers up to 18021 share no factor with it.
- 4
The digits of 18021 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 40 steps to reach 1.
LaTeX source of the formulas on this page
\[ 18021 = 3 \times 6007 \]
18021 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 24032 |
| Euler totient φ(n) | 12012 |
| Square | 324756441 |
| Cube | 5852435823261 |
| Square root | 134.242318 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 40 |
| Scientific notation | 1.8021 × |
18021 in other forms
| Form | Value |
|---|---|
| In words | eighteen thousand and twenty-one |
| Binary (base 2) | 100011001100101 |
| Octal (base 8) | 43145 |
| Hexadecimal (base 16) | 4665 |
| Base 3 | 220201110 |
| As time | 18021 seconds = 5 h 0 min 21 s |
Is 18021 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 | Yes (18021 ÷ 3 = 6007) | 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 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 18021 a prime number?
No. 18021 = 3 × 6007, so it is divisible by 3.
What are the factors of 18021?
1, 3, 6007, 18021.
What is 18021 in binary?
100011001100101 (hexadecimal 4665, octal 43145).
What is the square root of 18021?
About 134.2423.
Is 18021 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 18021?
18021 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 6007, the product of two primes.