The number 21249
21249 is a composite number with 8 divisors. Its prime factorisation is × 787. Divisors (8): 1, 3, 9, 27, 787, 2361, 7083, 21249.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21249 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21249 is composite. Its prime factorisation is
- 3
The divisors add up to 31520; without 21249 itself that is 10271, so 21249 is deficient (10271 is less than 21249). Euler's totient φ(21249) = 14148 numbers up to 21249 share no factor with it.
- 4
The digits of 21249 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21249 = 3^{3} \times 787 \]21249 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 31520 |
| Euler totient φ(n) | 14148 |
| Square | 451520001 |
| Cube | 9594348501249 |
| Square root | 145.770367 (= 3√2361) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 56 |
| Scientific notation | 2.1249 × |
21249 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and forty-nine |
| Binary (base 2) | 101001100000001 |
| Octal (base 8) | 51401 |
| Hexadecimal (base 16) | 5301 |
| Base 3 | 1002011000 |
| As time | 21249 seconds = 5 h 54 min 9 s |
Is 21249 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 | Yes (21249 ÷ 3 = 7083) | 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 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 | No (remainder 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21249 ÷ 9 = 2361) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | 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 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21249 a prime number?
No. 21249 = × 787, so it is divisible by 3.
What are the factors of 21249?
1, 3, 9, 27, 787, 2361, 7083, 21249.
What is 21249 in binary?
101001100000001 (hexadecimal 5301, octal 51401).
What is the square root of 21249?
About 145.7704, exactly 3√2361.
Is 21249 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21249?
It is a composite number with 8 divisors.