The number 77920
77920 is a composite number with 24 divisors. Its prime factorisation is × 5 × 487. Divisors (24): 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 487, 974, 1948, 2435 … 77920.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
77920 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
77920 is composite. Its prime factorisation is
- 3
The divisors add up to 184464; without 77920 itself that is 106544, so 77920 is abundant (106544 is more than 77920). Euler's totient φ(77920) = 31104 numbers up to 77920 share no factor with it.
- 4
The digits of 77920 add up to 25, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 138 steps to reach 1.
LaTeX source of the formulas on this page
\[ 77920 = 2^{5} \times 5 \times 487 \]77920 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 184464 |
| Euler totient φ(n) | 31104 |
| Square | 6071526400 |
| Cube | 473093337088000 |
| Square root | 279.141541 (= 4√4870) |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 138 |
| Scientific notation | 7.792 × |
77920 in other forms
| Form | Value |
|---|---|
| In words | seventy-seven thousand nine hundred and twenty |
| Binary (base 2) | 10011000001100000 |
| Octal (base 8) | 230140 |
| Hexadecimal (base 16) | 13060 |
| Base 3 | 10221212221 |
| As time | 77920 seconds = 21 h 38 min 40 s |
Is 77920 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (77920 ÷ 2 = 38960) | 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 (77920 ÷ 4 = 19480) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (77920 ÷ 5 = 15584) | 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 | Yes (77920 ÷ 8 = 9740) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (77920 ÷ 10 = 7792) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | 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 77920 a prime number?
No. 77920 = × 5 × 487, so it is divisible by 2.
What are the factors of 77920?
1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 487, 974, 1948, 2435, 3896, 4870, 7792, 9740, 15584, 19480, 38960, 77920.
What is 77920 in binary?
10011000001100000 (hexadecimal 13060, octal 230140).
What is the square root of 77920?
About 279.1415, exactly 4√4870.
Is 77920 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 77920?
It is a composite number with 24 divisors.