The number 7990
7990 is a composite number with 16 divisors. Its prime factorisation is 2 × 5 × 17 × 47. Divisors (16): 1, 2, 5, 10, 17, 34, 47, 85, 94, 170, 235, 470, 799, 1598, 3995, 7990.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
7990 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
7990 is composite. Its prime factorisation is
- 3
The divisors add up to 15552; without 7990 itself that is 7562, so 7990 is deficient (7562 is less than 7990). Euler's totient φ(7990) = 2944 numbers up to 7990 share no factor with it.
- 4
The digits of 7990 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 83 steps to reach 1.
LaTeX source of the formulas on this page
\[ 7990 = 2 \times 5 \times 17 \times 47 \]
7990 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 15552 |
| Euler totient φ(n) | 2944 |
| Square | 63840100 |
| Cube | 510082399000 |
| Square root | 89.386800 |
| Digit sum / digital root | 25 / 7 |
| Collatz steps to 1 | 83 |
| Scientific notation | 7.99 × |
7990 in other forms
| Form | Value |
|---|---|
| In words | seven thousand nine hundred and ninety |
| Binary (base 2) | 1111100110110 |
| Octal (base 8) | 17466 |
| Hexadecimal (base 16) | 1F36 |
| Base 3 | 101221221 |
| As time | 7990 seconds = 2 h 13 min 10 s |
Is 7990 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (7990 ÷ 2 = 3995) | 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 | Yes (7990 ÷ 5 = 1598) | 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 6) | 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 (7990 ÷ 10 = 799) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 4) | 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 7990 a prime number?
No. 7990 = 2 × 5 × 17 × 47, so it is divisible by 2.
What are the factors of 7990?
1, 2, 5, 10, 17, 34, 47, 85, 94, 170, 235, 470, 799, 1598, 3995, 7990.
What is 7990 in binary?
1111100110110 (hexadecimal 1F36, octal 17466).
What is the square root of 7990?
About 89.3868.
Is 7990 divisible by 3?
No. Its digits add up to 25, which is not a multiple of 3.
What is special about the number 7990?
It is a composite number with 16 divisors.