The number 21872
21872 is a composite number with 10 divisors. Its prime factorisation is × 1367. Divisors (10): 1, 2, 4, 8, 16, 1367, 2734, 5468, 10936, 21872.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21872 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21872 is composite. Its prime factorisation is
- 3
The divisors add up to 42408; without 21872 itself that is 20536, so 21872 is deficient (20536 is less than 21872). Euler's totient φ(21872) = 10928 numbers up to 21872 share no factor with it.
- 4
The digits of 21872 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21872 = 2^{4} \times 1367 \]21872 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 10 |
| Sum of divisors | 42408 |
| Euler totient φ(n) | 10928 |
| Square | 478384384 |
| Cube | 10463223246848 |
| Square root | 147.891852 (= 4√1367) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1872 × |
21872 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand eight hundred and seventy-two |
| Binary (base 2) | 101010101110000 |
| Octal (base 8) | 52560 |
| Hexadecimal (base 16) | 5570 |
| Base 3 | 1010000002 |
| As time | 21872 seconds = 6 h 4 min 32 s |
Is 21872 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21872 ÷ 2 = 10936) | 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 (21872 ÷ 4 = 5468) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 4) | 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 (21872 ÷ 8 = 2734) | 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 2) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | 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 21872 a prime number?
No. 21872 = × 1367, so it is divisible by 2.
What are the factors of 21872?
1, 2, 4, 8, 16, 1367, 2734, 5468, 10936, 21872.
What is 21872 in binary?
101010101110000 (hexadecimal 5570, octal 52560).
What is the square root of 21872?
About 147.8919, exactly 4√1367.
Is 21872 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 21872?
It is a composite number with 10 divisors.