The number 21125
21125 is a composite number with 12 divisors. Its prime factorisation is Ć . Divisors (12): 1, 5, 13, 25, 65, 125, 169, 325, 845, 1625, 4225, 21125.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21125 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21125 is composite. Its prime factorisation is
- 3
The divisors add up to 28548; without 21125 itself that is 7423, so 21125 is deficient (7423 is less than 21125). Euler's totient Ļ(21125) = 15600 numbers up to 21125 share no factor with it.
- 4
The digits of 21125 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21125 = 5^{3} \times 13^{2} \]21125 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 28548 |
| Euler totient Ļ(n) | 15600 |
| Square | 446265625 |
| Cube | 9427361328125 |
| Square root | 145.344419 (= 65ā5) |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1125 Ć |
21125 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and twenty-five |
| Binary (base 2) | 101001010000101 |
| Octal (base 8) | 51205 |
| Hexadecimal (base 16) | 5285 |
| Base 3 | 1001222102 |
| As time | 21125 seconds = 5 h 52 min 5 s |
Is 21125 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 2) | 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 (21125 Ć· 5 = 4225) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | 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 2) | 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 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21125 a prime number?
No. 21125 = Ć , so it is divisible by 5.
What are the factors of 21125?
1, 5, 13, 25, 65, 125, 169, 325, 845, 1625, 4225, 21125.
What is 21125 in binary?
101001010000101 (hexadecimal 5285, octal 51205).
What is the square root of 21125?
About 145.3444, exactly 65ā5.
Is 21125 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 21125?
It is a composite number with 12 divisors.