The number 778
778 is a composite number with 4 divisors. Its prime factorisation is 2 × 389. Divisors (4): 1, 2, 389, 778.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 778: a semiprime: 2 × 389, the product of two primes.
- 2
778 is composite. Its prime factorisation is
- 3
The divisors add up to 1170; without 778 itself that is 392, so 778 is deficient (392 is less than 778). Euler's totient φ(778) = 388 numbers up to 778 share no factor with it.
- 4
The digits of 778 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 121 steps to reach 1.
LaTeX source of the formulas on this page
\[ 778 = 2 \times 389 \]
778 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1170 |
| Euler totient φ(n) | 388 |
| Square | 605284 |
| Cube | 470910952 |
| Square root | 27.892651 |
| Digit sum / digital root | 22 / 4 |
| Collatz steps to 1 | 121 |
| Scientific notation | 7.78 × |
778 in other forms
| Form | Value |
|---|---|
| In words | seven hundred and seventy-eight |
| Roman numerals | DCCLXXVIII |
| Binary (base 2) | 1100001010 |
| Octal (base 8) | 1412 |
| Hexadecimal (base 16) | 30A |
| Base 3 | 1001211 |
| As time | 778 seconds = 12 min 58 s |
Is 778 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (778 ÷ 2 = 389) | 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 | 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 | No (remainder 4) | 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 2) | 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 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 10) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 778 a prime number?
No. 778 = 2 × 389, so it is divisible by 2.
What are the factors of 778?
1, 2, 389, 778.
What is 778 in binary?
1100001010 (hexadecimal 30A, octal 1412).
What is the square root of 778?
About 27.8927.
What is 778 in Roman numerals?
DCCLXXVIII.
Is 778 divisible by 3?
No. Its digits add up to 22, which is not a multiple of 3.
What is special about the number 778?
778 is a semiprime: 2 × 389, the product of two primes.