The number 8720
8720 is a composite number with 20 divisors. Its prime factorisation is × 5 × 109. Divisors (20): 1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 109, 218, 436, 545, 872, 1090 … 8720.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
8720 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
8720 is composite. Its prime factorisation is
- 3
The divisors add up to 20460; without 8720 itself that is 11740, so 8720 is abundant (11740 is more than 8720). Euler's totient φ(8720) = 3456 numbers up to 8720 share no factor with it.
- 4
The digits of 8720 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 47 steps to reach 1.
LaTeX source of the formulas on this page
\[ 8720 = 2^{4} \times 5 \times 109 \]8720 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 20 |
| Sum of divisors | 20460 |
| Euler totient φ(n) | 3456 |
| Square | 76038400 |
| Cube | 663054848000 |
| Square root | 93.380940 (= 4√545) |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 47 |
| Scientific notation | 8.72 × |
8720 in other forms
| Form | Value |
|---|---|
| In words | eight thousand seven hundred and twenty |
| Binary (base 2) | 10001000010000 |
| Octal (base 8) | 21020 |
| Hexadecimal (base 16) | 2210 |
| Base 3 | 102221222 |
| As time | 8720 seconds = 2 h 25 min 20 s |
Is 8720 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (8720 ÷ 2 = 4360) | 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 | Yes (8720 ÷ 4 = 2180) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (8720 ÷ 5 = 1744) | 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 5) | 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 (8720 ÷ 8 = 1090) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (8720 ÷ 10 = 872) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 8720 a prime number?
No. 8720 = × 5 × 109, so it is divisible by 2.
What are the factors of 8720?
1, 2, 4, 5, 8, 10, 16, 20, 40, 80, 109, 218, 436, 545, 872, 1090, 1744, 2180, 4360, 8720.
What is 8720 in binary?
10001000010000 (hexadecimal 2210, octal 21020).
What is the square root of 8720?
About 93.3809, exactly 4√545.
Is 8720 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 8720?
It is a composite number with 20 divisors.