The number 18720
18720 is a composite number with 72 divisors. Its prime factorisation is × × 5 × 13. Divisors (72): 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 13, 15, 16, 18, 20, 24 … 18720.
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How to work it out
- 1
What is special about 18720: a Harshad number: divisible by its digit sum 18.
- 2
18720 is composite. Its prime factorisation is
- 3
The divisors add up to 68796; without 18720 itself that is 50076, so 18720 is abundant (50076 is more than 18720). Euler's totient φ(18720) = 4608 numbers up to 18720 share no factor with it.
- 4
The digits of 18720 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 61 steps to reach 1.
LaTeX source of the formulas on this page
\[ 18720 = 2^{5} \times 3^{2} \times 5 \times 13 \]18720 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 72 |
| Sum of divisors | 68796 |
| Euler totient φ(n) | 4608 |
| Square | 350438400 |
| Cube | 6560206848000 |
| Square root | 136.821051 (= 12√130) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 61 |
| Scientific notation | 1.872 × |
18720 in other forms
| Form | Value |
|---|---|
| In words | eighteen thousand seven hundred and twenty |
| Binary (base 2) | 100100100100000 |
| Octal (base 8) | 44440 |
| Hexadecimal (base 16) | 4920 |
| Base 3 | 221200100 |
| As time | 18720 seconds = 5 h 12 min 0 s |
Is 18720 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (18720 ÷ 2 = 9360) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (18720 ÷ 3 = 6240) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (18720 ÷ 4 = 4680) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (18720 ÷ 5 = 3744) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (18720 ÷ 6 = 3120) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 | Yes (18720 ÷ 8 = 2340) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (18720 ÷ 9 = 2080) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (18720 ÷ 10 = 1872) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (18720 ÷ 12 = 1560) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 18720 a prime number?
No. 18720 = × × 5 × 13, so it is divisible by 2.
What are the factors of 18720?
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 13, 15, 16, 18, 20, 24, 26, 30, 32, 36, 39, 40, 45, 48, 52, 60, 65, 72, 78, 80, 90, 96, 104, 117, 120, 130, 144, 156, 160, 180, 195, 208, 234, 240, 260, 288, 312, 360, 390, 416, 468, 480, 520, 585, 624, 720, 780, 936, 1040, 1170, 1248, 1440, 1560, 1872, 2080, 2340, 3120, 3744, 4680, 6240, 9360, 18720.
What is 18720 in binary?
100100100100000 (hexadecimal 4920, octal 44440).
What is the square root of 18720?
About 136.8211, exactly 12√130.
Is 18720 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 18720?
18720 is a Harshad number: divisible by its digit sum 18.