The number 77991
77991 is a composite number with 4 divisors. Its prime factorisation is 3 × 25997. Divisors (4): 1, 3, 25997, 77991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 77991: a semiprime: 3 × 25997, the product of two primes.
- 2
77991 is composite. Its prime factorisation is
- 3
The divisors add up to 103992; without 77991 itself that is 26001, so 77991 is deficient (26001 is less than 77991). Euler's totient φ(77991) = 51992 numbers up to 77991 share no factor with it.
- 4
The digits of 77991 add up to 33, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 156 steps to reach 1.
LaTeX source of the formulas on this page
\[ 77991 = 3 \times 25997 \]
77991 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 103992 |
| Euler totient φ(n) | 51992 |
| Square | 6082596081 |
| Cube | 474387750953271 |
| Square root | 279.268688 |
| Digit sum / digital root | 33 / 6 |
| Collatz steps to 1 | 156 |
| Scientific notation | 7.7991 × |
77991 in other forms
| Form | Value |
|---|---|
| In words | seventy-seven thousand nine hundred and ninety-one |
| Binary (base 2) | 10011000010100111 |
| Octal (base 8) | 230247 |
| Hexadecimal (base 16) | 130A7 |
| Base 3 | 10221222120 |
| As time | 77991 seconds = 21 h 39 min 51 s |
Is 77991 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 (77991 ÷ 3 = 25997) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | 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 4) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | 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 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 77991 a prime number?
No. 77991 = 3 × 25997, so it is divisible by 3.
What are the factors of 77991?
1, 3, 25997, 77991.
What is 77991 in binary?
10011000010100111 (hexadecimal 130A7, octal 230247).
What is the square root of 77991?
About 279.2687.
Is 77991 divisible by 3?
Yes. Its digits add up to 33, a multiple of 3.
What is special about the number 77991?
77991 is a semiprime: 3 × 25997, the product of two primes.