The number 21219
21219 is a composite number with 8 divisors. Its prime factorisation is 3 × 11 × 643. Divisors (8): 1, 3, 11, 33, 643, 1929, 7073, 21219.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21219: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21219 is composite. Its prime factorisation is
- 3
The divisors add up to 30912; without 21219 itself that is 9693, so 21219 is deficient (9693 is less than 21219). Euler's totient φ(21219) = 12840 numbers up to 21219 share no factor with it.
- 4
The digits of 21219 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 30 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21219 = 3 \times 11 \times 643 \]
21219 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 30912 |
| Euler totient φ(n) | 12840 |
| Square | 450245961 |
| Cube | 9553769046459 |
| Square root | 145.667429 |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 30 |
| Scientific notation | 2.1219 × |
21219 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and nineteen |
| Binary (base 2) | 101001011100011 |
| Octal (base 8) | 51343 |
| Hexadecimal (base 16) | 52E3 |
| Base 3 | 1002002220 |
| As time | 21219 seconds = 5 h 53 min 39 s |
Is 21219 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 (21219 ÷ 3 = 7073) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | 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 2) | 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 3) | 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 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (21219 ÷ 11 = 1929) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21219 a prime number?
No. 21219 = 3 × 11 × 643, so it is divisible by 3.
What are the factors of 21219?
1, 3, 11, 33, 643, 1929, 7073, 21219.
What is 21219 in binary?
101001011100011 (hexadecimal 52E3, octal 51343).
What is the square root of 21219?
About 145.6674.
Is 21219 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 21219?
21219 is a happy number: repeatedly adding the squares of its digits reaches 1.