The number 21189
21189 is a composite number with 8 divisors. Its prime factorisation is 3 × 7 × 1009. Divisors (8): 1, 3, 7, 21, 1009, 3027, 7063, 21189.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21189: a Harshad number: divisible by its digit sum 21.
- 2
21189 is composite. Its prime factorisation is
- 3
The divisors add up to 32320; without 21189 itself that is 11131, so 21189 is deficient (11131 is less than 21189). Euler's totient φ(21189) = 12096 numbers up to 21189 share no factor with it.
- 4
The digits of 21189 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 100 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21189 = 3 \times 7 \times 1009 \]
21189 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 32320 |
| Euler totient φ(n) | 12096 |
| Square | 448973721 |
| Cube | 9513304174269 |
| Square root | 145.564419 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 100 |
| Scientific notation | 2.1189 × |
21189 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand one hundred and eighty-nine |
| Binary (base 2) | 101001011000101 |
| Octal (base 8) | 51305 |
| Hexadecimal (base 16) | 52C5 |
| Base 3 | 1002001210 |
| As time | 21189 seconds = 5 h 53 min 9 s |
Is 21189 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 (21189 ÷ 3 = 7063) | 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 | Yes (21189 ÷ 7 = 3027) | 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 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 3) | 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 21189 a prime number?
No. 21189 = 3 × 7 × 1009, so it is divisible by 3.
What are the factors of 21189?
1, 3, 7, 21, 1009, 3027, 7063, 21189.
What is 21189 in binary?
101001011000101 (hexadecimal 52C5, octal 51305).
What is the square root of 21189?
About 145.5644.
Is 21189 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 21189?
21189 is a Harshad number: divisible by its digit sum 21.