The number 21228
21228 is a composite number with 24 divisors. Its prime factorisation is × 3 × 29 × 61. Divisors (24): 1, 2, 3, 4, 6, 12, 29, 58, 61, 87, 116, 122, 174, 183, 244, 348 … 21228.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
21228 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
21228 is composite. Its prime factorisation is
- 3
The divisors add up to 52080; without 21228 itself that is 30852, so 21228 is abundant (30852 is more than 21228). Euler's totient φ(21228) = 6720 numbers up to 21228 share no factor with it.
- 4
The digits of 21228 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21228 = 2^{2} \times 3 \times 29 \times 61 \]21228 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 52080 |
| Euler totient φ(n) | 6720 |
| Square | 450627984 |
| Cube | 9565930844352 |
| Square root | 145.698318 (= 2√5307) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.1228 × |
21228 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and twenty-eight |
| Binary (base 2) | 101001011101100 |
| Octal (base 8) | 51354 |
| Hexadecimal (base 16) | 52EC |
| Base 3 | 1002010020 |
| As time | 21228 seconds = 5 h 53 min 48 s |
Is 21228 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21228 ÷ 2 = 10614) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21228 ÷ 3 = 7076) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (21228 ÷ 4 = 5307) | 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 | Yes (21228 ÷ 6 = 3538) | 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 4) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | 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 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (21228 ÷ 12 = 1769) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21228 a prime number?
No. 21228 = × 3 × 29 × 61, so it is divisible by 2.
What are the factors of 21228?
1, 2, 3, 4, 6, 12, 29, 58, 61, 87, 116, 122, 174, 183, 244, 348, 366, 732, 1769, 3538, 5307, 7076, 10614, 21228.
What is 21228 in binary?
101001011101100 (hexadecimal 52EC, octal 51354).
What is the square root of 21228?
About 145.6983, exactly 2√5307.
Is 21228 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21228?
It is a composite number with 24 divisors.