The number 1985
1985 is a composite number with 4 divisors. Its prime factorisation is 5 × 397. Divisors (4): 1, 5, 397, 1985.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1985: a semiprime: 5 × 397, the product of two primes.
- 2
1985 is composite. Its prime factorisation is
- 3
The divisors add up to 2388; without 1985 itself that is 403, so 1985 is deficient (403 is less than 1985). Euler's totient φ(1985) = 1584 numbers up to 1985 share no factor with it.
- 4
The digits of 1985 add up to 23, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 50 steps to reach 1.
LaTeX source of the formulas on this page
\[ 1985 = 5 \times 397 \]
1985 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 2388 |
| Euler totient φ(n) | 1584 |
| Square | 3940225 |
| Cube | 7821346625 |
| Square root | 44.553339 |
| Digit sum / digital root | 23 / 5 |
| Collatz steps to 1 | 50 |
| Scientific notation | 1.985 × |
1985 in other forms
| Form | Value |
|---|---|
| In words | one thousand nine hundred and eighty-five |
| Roman numerals | MCMLXXXV |
| Binary (base 2) | 11111000001 |
| Octal (base 8) | 3701 |
| Hexadecimal (base 16) | 7C1 |
| Base 3 | 2201112 |
| As time | 1985 seconds = 33 min 5 s |
Is 1985 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 2) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (1985 ÷ 5 = 397) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1985 a prime number?
No. 1985 = 5 × 397, so it is divisible by 5.
What are the factors of 1985?
1, 5, 397, 1985.
What is 1985 in binary?
11111000001 (hexadecimal 7C1, octal 3701).
What is the square root of 1985?
About 44.5533.
What is 1985 in Roman numerals?
MCMLXXXV.
Is 1985 divisible by 3?
No. Its digits add up to 23, which is not a multiple of 3.
What is special about the number 1985?
1985 is a semiprime: 5 × 397, the product of two primes.