The number 7900
7900 is a composite number with 18 divisors. Its prime factorisation is × × 79. Divisors (18): 1, 2, 4, 5, 10, 20, 25, 50, 79, 100, 158, 316, 395, 790, 1580, 1975 … 7900.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 7900: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
7900 is composite. Its prime factorisation is
- 3
The divisors add up to 17360; without 7900 itself that is 9460, so 7900 is abundant (9460 is more than 7900). Euler's totient φ(7900) = 3120 numbers up to 7900 share no factor with it.
- 4
The digits of 7900 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 39 steps to reach 1.
LaTeX source of the formulas on this page
\[ 7900 = 2^{2} \times 5^{2} \times 79 \]7900 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 18 |
| Sum of divisors | 17360 |
| Euler totient φ(n) | 3120 |
| Square | 62410000 |
| Cube | 493039000000 |
| Square root | 88.881944 (= 10√79) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 39 |
| Scientific notation | 7.9 × |
7900 in other forms
| Form | Value |
|---|---|
| In words | seven thousand nine hundred |
| Binary (base 2) | 1111011011100 |
| Octal (base 8) | 17334 |
| Hexadecimal (base 16) | 1EDC |
| Base 3 | 101211121 |
| As time | 7900 seconds = 2 h 11 min 40 s |
Is 7900 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (7900 ÷ 2 = 3950) | 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 (7900 ÷ 4 = 1975) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (7900 ÷ 5 = 1580) | 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 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 4) | 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 (7900 ÷ 10 = 790) | 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 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 7900 a prime number?
No. 7900 = × × 79, so it is divisible by 2.
What are the factors of 7900?
1, 2, 4, 5, 10, 20, 25, 50, 79, 100, 158, 316, 395, 790, 1580, 1975, 3950, 7900.
What is 7900 in binary?
1111011011100 (hexadecimal 1EDC, octal 17334).
What is the square root of 7900?
About 88.8819, exactly 10√79.
Is 7900 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 7900?
7900 is a happy number: repeatedly adding the squares of its digits reaches 1.