The number 21500
21500 is a composite number with 24 divisors. Its prime factorisation is × × 43. Divisors (24): 1, 2, 4, 5, 10, 20, 25, 43, 50, 86, 100, 125, 172, 215, 250, 430 … 21500.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21500 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21500 is composite. Its prime factorisation is
- 3
The divisors add up to 48048; without 21500 itself that is 26548, so 21500 is abundant (26548 is more than 21500). Euler's totient φ(21500) = 8400 numbers up to 21500 share no factor with it.
- 4
The digits of 21500 add up to 8, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21500 = 2^{2} \times 5^{3} \times 43 \]21500 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 48048 |
| Euler totient φ(n) | 8400 |
| Square | 462250000 |
| Cube | 9938375000000 |
| Square root | 146.628783 (= 10√215) |
| Digit sum / digital root | 8 / 8 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.15 × |
21500 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand five hundred |
| Binary (base 2) | 101001111111100 |
| Octal (base 8) | 51774 |
| Hexadecimal (base 16) | 53FC |
| Base 3 | 1002111022 |
| As time | 21500 seconds = 5 h 58 min 20 s |
Is 21500 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21500 ÷ 2 = 10750) | 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 (21500 ÷ 4 = 5375) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21500 ÷ 5 = 4300) | 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 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 4) | 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 (21500 ÷ 10 = 2150) | 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 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21500 a prime number?
No. 21500 = × × 43, so it is divisible by 2.
What are the factors of 21500?
1, 2, 4, 5, 10, 20, 25, 43, 50, 86, 100, 125, 172, 215, 250, 430, 500, 860, 1075, 2150, 4300, 5375, 10750, 21500.
What is 21500 in binary?
101001111111100 (hexadecimal 53FC, octal 51774).
What is the square root of 21500?
About 146.6288, exactly 10√215.
Is 21500 divisible by 3?
No. Its digits add up to 8, which is not a multiple of 3.
What is special about the number 21500?
It is a composite number with 24 divisors.