The number 7780
7780 is a composite number with 12 divisors. Its prime factorisation is × 5 × 389. Divisors (12): 1, 2, 4, 5, 10, 20, 389, 778, 1556, 1945, 3890, 7780.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
7780 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
7780 is composite. Its prime factorisation is
- 3
The divisors add up to 16380; without 7780 itself that is 8600, so 7780 is abundant (8600 is more than 7780). Euler's totient φ(7780) = 3104 numbers up to 7780 share no factor with it.
- 4
The digits of 7780 add up to 22, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 39 steps to reach 1.
LaTeX source of the formulas on this page
\[ 7780 = 2^{2} \times 5 \times 389 \]7780 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 16380 |
| Euler totient φ(n) | 3104 |
| Square | 60528400 |
| Cube | 470910952000 |
| Square root | 88.204308 (= 2√1945) |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 39 |
| Scientific notation | 7.78 × |
7780 in other forms
| Form | Value |
|---|---|
| In words | seven thousand seven hundred and eighty |
| Binary (base 2) | 1111001100100 |
| Octal (base 8) | 17144 |
| Hexadecimal (base 16) | 1E64 |
| Base 3 | 101200011 |
| As time | 7780 seconds = 2 h 9 min 40 s |
Is 7780 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (7780 ÷ 2 = 3890) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (7780 ÷ 4 = 1945) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (7780 ÷ 5 = 1556) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 4) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (7780 ÷ 10 = 778) | 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 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 7780 a prime number?
No. 7780 = × 5 × 389, so it is divisible by 2.
What are the factors of 7780?
1, 2, 4, 5, 10, 20, 389, 778, 1556, 1945, 3890, 7780.
What is 7780 in binary?
1111001100100 (hexadecimal 1E64, octal 17144).
What is the square root of 7780?
About 88.2043, exactly 2√1945.
Is 7780 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 7780?
It is a composite number with 12 divisors.