The number 3990
3990 is a composite number with 32 divisors. Its prime factorisation is 2 × 3 × 5 × 7 × 19. Divisors (32): 1, 2, 3, 5, 6, 7, 10, 14, 15, 19, 21, 30, 35, 38, 42, 57 … 3990.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 3990: a Harshad number: divisible by its digit sum 21.
- 2
3990 is composite. Its prime factorisation is
- 3
The divisors add up to 11520; without 3990 itself that is 7530, so 3990 is abundant (7530 is more than 3990). Euler's totient φ(3990) = 864 numbers up to 3990 share no factor with it.
- 4
The digits of 3990 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 51 steps to reach 1.
LaTeX source of the formulas on this page
\[ 3990 = 2 \times 3 \times 5 \times 7 \times 19 \]
3990 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 11520 |
| Euler totient φ(n) | 864 |
| Square | 15920100 |
| Cube | 63521199000 |
| Square root | 63.166447 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 51 |
| Scientific notation | 3.99 × |
3990 in other forms
| Form | Value |
|---|---|
| In words | three thousand nine hundred and ninety |
| Roman numerals | MMMCMXC |
| Binary (base 2) | 111110010110 |
| Octal (base 8) | 7626 |
| Hexadecimal (base 16) | F96 |
| Base 3 | 12110210 |
| As time | 3990 seconds = 1 h 6 min 30 s |
Is 3990 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (3990 ÷ 2 = 1995) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (3990 ÷ 3 = 1330) | 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 (3990 ÷ 5 = 798) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (3990 ÷ 6 = 665) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (3990 ÷ 7 = 570) | 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 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (3990 ÷ 10 = 399) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 8) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 3990 a prime number?
No. 3990 = 2 × 3 × 5 × 7 × 19, so it is divisible by 2.
What are the factors of 3990?
1, 2, 3, 5, 6, 7, 10, 14, 15, 19, 21, 30, 35, 38, 42, 57, 70, 95, 105, 114, 133, 190, 210, 266, 285, 399, 570, 665, 798, 1330, 1995, 3990.
What is 3990 in binary?
111110010110 (hexadecimal F96, octal 7626).
What is the square root of 3990?
About 63.1664.
What is 3990 in Roman numerals?
MMMCMXC.
Is 3990 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 3990?
3990 is a Harshad number: divisible by its digit sum 21.