The number 7999
7999 is a composite number with 4 divisors. Its prime factorisation is 19 × 421. Divisors (4): 1, 19, 421, 7999.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 7999: a semiprime: 19 × 421, the product of two primes.
- 2
7999 is composite. Its prime factorisation is
- 3
The divisors add up to 8440; without 7999 itself that is 441, so 7999 is deficient (441 is less than 7999). Euler's totient φ(7999) = 7560 numbers up to 7999 share no factor with it.
- 4
The digits of 7999 add up to 34, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 189 steps to reach 1.
LaTeX source of the formulas on this page
\[ 7999 = 19 \times 421 \]
7999 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 8440 |
| Euler totient φ(n) | 7560 |
| Square | 63984001 |
| Cube | 511808023999 |
| Square root | 89.437129 |
| Digit sum / digital root | 34 / 7 |
| Collatz steps to 1 | 189 |
| Scientific notation | 7.999 × |
7999 in other forms
| Form | Value |
|---|---|
| In words | seven thousand nine hundred and ninety-nine |
| Binary (base 2) | 1111100111111 |
| Octal (base 8) | 17477 |
| Hexadecimal (base 16) | 1F3F |
| Base 3 | 101222021 |
| As time | 7999 seconds = 2 h 13 min 19 s |
Is 7999 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 | No (remainder 1) | 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 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 7999 a prime number?
No. 7999 = 19 × 421, so it is divisible by 19.
What are the factors of 7999?
1, 19, 421, 7999.
What is 7999 in binary?
1111100111111 (hexadecimal 1F3F, octal 17477).
What is the square root of 7999?
About 89.4371.
Is 7999 divisible by 3?
No. Its digits add up to 34, which is not a multiple of 3.
What is special about the number 7999?
7999 is a semiprime: 19 × 421, the product of two primes.