The number 7940
7940 is a composite number with 12 divisors. Its prime factorisation is × 5 × 397. Divisors (12): 1, 2, 4, 5, 10, 20, 397, 794, 1588, 1985, 3970, 7940.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 7940: a Harshad number: divisible by its digit sum 20.
- 2
7940 is composite. Its prime factorisation is
- 3
The divisors add up to 16716; without 7940 itself that is 8776, so 7940 is abundant (8776 is more than 7940). Euler's totient φ(7940) = 3168 numbers up to 7940 share no factor with it.
- 4
The digits of 7940 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 52 steps to reach 1.
LaTeX source of the formulas on this page
\[ 7940 = 2^{2} \times 5 \times 397 \]7940 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 16716 |
| Euler totient φ(n) | 3168 |
| Square | 63043600 |
| Cube | 500566184000 |
| Square root | 89.106678 (= 2√1985) |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 52 |
| Scientific notation | 7.94 × |
7940 in other forms
| Form | Value |
|---|---|
| In words | seven thousand nine hundred and forty |
| Binary (base 2) | 1111100000100 |
| Octal (base 8) | 17404 |
| Hexadecimal (base 16) | 1F04 |
| Base 3 | 101220002 |
| As time | 7940 seconds = 2 h 12 min 20 s |
Is 7940 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (7940 ÷ 2 = 3970) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (7940 ÷ 4 = 1985) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (7940 ÷ 5 = 1588) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 2) | 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 2) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (7940 ÷ 10 = 794) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 8) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 7940 a prime number?
No. 7940 = × 5 × 397, so it is divisible by 2.
What are the factors of 7940?
1, 2, 4, 5, 10, 20, 397, 794, 1588, 1985, 3970, 7940.
What is 7940 in binary?
1111100000100 (hexadecimal 1F04, octal 17404).
What is the square root of 7940?
About 89.1067, exactly 2√1985.
Is 7940 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 7940?
7940 is a Harshad number: divisible by its digit sum 20.