The number 78428
78428 is a composite number with 12 divisors. Its prime factorisation is × 7 × 2801. Divisors (12): 1, 2, 4, 7, 14, 28, 2801, 5602, 11204, 19607, 39214, 78428.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
78428 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
78428 is composite. Its prime factorisation is
- 3
The divisors add up to 156912; without 78428 itself that is 78484, so 78428 is abundant (78484 is more than 78428). Euler's totient φ(78428) = 33600 numbers up to 78428 share no factor with it.
- 4
The digits of 78428 add up to 29, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 138 steps to reach 1.
LaTeX source of the formulas on this page
\[ 78428 = 2^{2} \times 7 \times 2801 \]78428 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 156912 |
| Euler totient φ(n) | 33600 |
| Square | 6150951184 |
| Cube | 482406799458752 |
| Square root | 280.049996 (= 2√19607) |
| Digit sum / digital root | 29 / 2 |
| Collatz steps to 1 | 138 |
| Scientific notation | 7.8428 × |
78428 in other forms
| Form | Value |
|---|---|
| In words | seventy-eight thousand four hundred and twenty-eight |
| Binary (base 2) | 10011001001011100 |
| Octal (base 8) | 231134 |
| Hexadecimal (base 16) | 1325C |
| Base 3 | 10222120202 |
| As time | 78428 seconds = 21 h 47 min 8 s |
Is 78428 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (78428 ÷ 2 = 39214) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (78428 ÷ 4 = 19607) | 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 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (78428 ÷ 7 = 11204) | 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 2) | 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 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 78428 a prime number?
No. 78428 = × 7 × 2801, so it is divisible by 2.
What are the factors of 78428?
1, 2, 4, 7, 14, 28, 2801, 5602, 11204, 19607, 39214, 78428.
What is 78428 in binary?
10011001001011100 (hexadecimal 1325C, octal 231134).
What is the square root of 78428?
About 280.0500, exactly 2√19607.
Is 78428 divisible by 3?
No. Its digits add up to 29, which is not a multiple of 3.
What is special about the number 78428?
It is a composite number with 12 divisors.