The number 21078
21078 is a composite number with 12 divisors. Its prime factorisation is 2 × × 1171. Divisors (12): 1, 2, 3, 6, 9, 18, 1171, 2342, 3513, 7026, 10539, 21078.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21078: a Harshad number: divisible by its digit sum 18.
- 2
21078 is composite. Its prime factorisation is
- 3
The divisors add up to 45708; without 21078 itself that is 24630, so 21078 is abundant (24630 is more than 21078). Euler's totient φ(21078) = 7020 numbers up to 21078 share no factor with it.
- 4
The digits of 21078 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 193 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21078 = 2 \times 3^{2} \times 1171 \]21078 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 45708 |
| Euler totient φ(n) | 7020 |
| Square | 444282084 |
| Cube | 9364577766552 |
| Square root | 145.182644 (= 3√2342) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 193 |
| Scientific notation | 2.1078 × |
21078 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand and seventy-eight |
| Binary (base 2) | 101001001010110 |
| Octal (base 8) | 51126 |
| Hexadecimal (base 16) | 5256 |
| Base 3 | 1001220200 |
| As time | 21078 seconds = 5 h 51 min 18 s |
Is 21078 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21078 ÷ 2 = 10539) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21078 ÷ 3 = 7026) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | 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 (21078 ÷ 6 = 3513) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (21078 ÷ 9 = 2342) | 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 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21078 a prime number?
No. 21078 = 2 × × 1171, so it is divisible by 2.
What are the factors of 21078?
1, 2, 3, 6, 9, 18, 1171, 2342, 3513, 7026, 10539, 21078.
What is 21078 in binary?
101001001010110 (hexadecimal 5256, octal 51126).
What is the square root of 21078?
About 145.1826, exactly 3√2342.
Is 21078 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 21078?
21078 is a Harshad number: divisible by its digit sum 18.