The number 78021
78021 is a composite number with 6 divisors. Its prime factorisation is × 8669. Divisors (6): 1, 3, 9, 8669, 26007, 78021.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
78021 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
78021 is composite. Its prime factorisation is
- 3
The divisors add up to 112710; without 78021 itself that is 34689, so 78021 is deficient (34689 is less than 78021). Euler's totient φ(78021) = 52008 numbers up to 78021 share no factor with it.
- 4
The digits of 78021 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 125 steps to reach 1.
LaTeX source of the formulas on this page
\[ 78021 = 3^{2} \times 8669 \]78021 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 112710 |
| Euler totient φ(n) | 52008 |
| Square | 6087276441 |
| Cube | 474935395203261 |
| Square root | 279.322394 (= 3√8669) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 125 |
| Scientific notation | 7.8021 × |
78021 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand and twenty-one |
| Binary (base 2) | 10011000011000101 |
| Octal (base 8) | 230305 |
| Hexadecimal (base 16) | 130C5 |
| Base 3 | 10222000200 |
| As time | 78021 seconds = 21 h 40 min 21 s |
Is 78021 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 (78021 ÷ 3 = 26007) | 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 1) | 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 6) | 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 | Yes (78021 ÷ 9 = 8669) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | 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 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 78021 a prime number?
No. 78021 = × 8669, so it is divisible by 3.
What are the factors of 78021?
1, 3, 9, 8669, 26007, 78021.
What is 78021 in binary?
10011000011000101 (hexadecimal 130C5, octal 230305).
What is the square root of 78021?
About 279.3224, exactly 3√8669.
Is 78021 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 78021?
It is a composite number with 6 divisors.