The number 21220
21220 is a composite number with 12 divisors. Its prime factorisation is × 5 × 1061. Divisors (12): 1, 2, 4, 5, 10, 20, 1061, 2122, 4244, 5305, 10610, 21220.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21220: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21220 is composite. Its prime factorisation is
- 3
The divisors add up to 44604; without 21220 itself that is 23384, so 21220 is abundant (23384 is more than 21220). Euler's totient φ(21220) = 8480 numbers up to 21220 share no factor with it.
- 4
The digits of 21220 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21220 = 2^{2} \times 5 \times 1061 \]21220 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 44604 |
| Euler totient φ(n) | 8480 |
| Square | 450288400 |
| Cube | 9555119848000 |
| Square root | 145.670862 (= 2√5305) |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.122 × |
21220 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and twenty |
| Binary (base 2) | 101001011100100 |
| Octal (base 8) | 51344 |
| Hexadecimal (base 16) | 52E4 |
| Base 3 | 1002002221 |
| As time | 21220 seconds = 5 h 53 min 40 s |
Is 21220 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21220 ÷ 2 = 10610) | 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 (21220 ÷ 4 = 5305) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21220 ÷ 5 = 4244) | 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 3) | 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 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21220 ÷ 10 = 2122) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | 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 21220 a prime number?
No. 21220 = × 5 × 1061, so it is divisible by 2.
What are the factors of 21220?
1, 2, 4, 5, 10, 20, 1061, 2122, 4244, 5305, 10610, 21220.
What is 21220 in binary?
101001011100100 (hexadecimal 52E4, octal 51344).
What is the square root of 21220?
About 145.6709, exactly 2√5305.
Is 21220 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 21220?
21220 is a happy number: repeatedly adding the squares of its digits reaches 1.