The number 21875
21875 is a composite number with 12 divisors. Its prime factorisation is × 7. Divisors (12): 1, 5, 7, 25, 35, 125, 175, 625, 875, 3125, 4375, 21875.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21875 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21875 is composite. Its prime factorisation is
- 3
The divisors add up to 31248; without 21875 itself that is 9373, so 21875 is deficient (9373 is less than 21875). Euler's totient φ(21875) = 15000 numbers up to 21875 share no factor with it.
- 4
The digits of 21875 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 162 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21875 = 5^{5} \times 7 \]21875 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 31248 |
| Euler totient φ(n) | 15000 |
| Square | 478515625 |
| Cube | 10467529296875 |
| Square root | 147.901995 (= 25√35) |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 162 |
| Scientific notation | 2.1875 × |
21875 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and seventy-five |
| Binary (base 2) | 101010101110011 |
| Octal (base 8) | 52563 |
| Hexadecimal (base 16) | 5573 |
| Base 3 | 1010000012 |
| As time | 21875 seconds = 6 h 4 min 35 s |
Is 21875 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21875 ÷ 5 = 4375) | 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 | Yes (21875 ÷ 7 = 3125) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | 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 7) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21875 a prime number?
No. 21875 = × 7, so it is divisible by 5.
What are the factors of 21875?
1, 5, 7, 25, 35, 125, 175, 625, 875, 3125, 4375, 21875.
What is 21875 in binary?
101010101110011 (hexadecimal 5573, octal 52563).
What is the square root of 21875?
About 147.9020, exactly 25√35.
Is 21875 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 21875?
It is a composite number with 12 divisors.