The number 21208
21208 is a composite number with 16 divisors. Its prime factorisation is × 11 × 241. Divisors (16): 1, 2, 4, 8, 11, 22, 44, 88, 241, 482, 964, 1928, 2651, 5302, 10604, 21208.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21208 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21208 is composite. Its prime factorisation is
- 3
The divisors add up to 43560; without 21208 itself that is 22352, so 21208 is abundant (22352 is more than 21208). Euler's totient φ(21208) = 9600 numbers up to 21208 share no factor with it.
- 4
The digits of 21208 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21208 = 2^{3} \times 11 \times 241 \]21208 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 43560 |
| Euler totient φ(n) | 9600 |
| Square | 449779264 |
| Cube | 9538918630912 |
| Square root | 145.629667 (= 2√5302) |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1208 × |
21208 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and eight |
| Binary (base 2) | 101001011011000 |
| Octal (base 8) | 51330 |
| Hexadecimal (base 16) | 52D8 |
| Base 3 | 1002002111 |
| As time | 21208 seconds = 5 h 53 min 28 s |
Is 21208 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21208 ÷ 2 = 10604) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21208 ÷ 4 = 5302) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 (21208 ÷ 8 = 2651) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21208 ÷ 11 = 1928) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21208 a prime number?
No. 21208 = × 11 × 241, so it is divisible by 2.
What are the factors of 21208?
1, 2, 4, 8, 11, 22, 44, 88, 241, 482, 964, 1928, 2651, 5302, 10604, 21208.
What is 21208 in binary?
101001011011000 (hexadecimal 52D8, octal 51330).
What is the square root of 21208?
About 145.6297, exactly 2√5302.
Is 21208 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 21208?
It is a composite number with 16 divisors.