The number 1999
1999 is a twin prime (1997 and 1999 are both prime) and the 303rd prime number. Its only divisors are 1 and 1999.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 1999: a twin prime (1997 and 1999 are both prime); the 303rd prime number.
- 2
1999 is prime, so its only factors are 1 and 1999. It is the 303rd prime; the next prime is 2003 and the one before is 1997.
- 3
The divisors add up to 2000; without 1999 itself that is 1, so 1999 is deficient (1 is less than 1999). Euler's totient φ(1999) = 1998 numbers up to 1999 share no factor with it.
- 4
The digits of 1999 add up to 28, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 50 steps to reach 1.
1999 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 2000 |
| Euler totient φ(n) | 1998 |
| Square | 3996001 |
| Cube | 7988005999 |
| Square root | 44.710178 |
| Digit sum / digital root | 28 / 1 |
| Collatz steps to 1 | 50 |
| Scientific notation | 1.999 × |
1999 in other forms
| Form | Value |
|---|---|
| In words | one thousand nine hundred and ninety-nine |
| Roman numerals | MCMXCIX |
| Binary (base 2) | 11111001111 |
| Octal (base 8) | 3717 |
| Hexadecimal (base 16) | 7CF |
| Base 3 | 2202001 |
| As time | 1999 seconds = 33 min 19 s |
Is 1999 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 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | 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 7) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | 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 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 1999 a prime number?
Yes. 1999 is divisible only by 1 and itself.
What are the factors of 1999?
1, 1999.
What is 1999 in binary?
11111001111 (hexadecimal 7CF, octal 3717).
What is the square root of 1999?
About 44.7102.
What is 1999 in Roman numerals?
MCMXCIX.
Is 1999 divisible by 3?
No. Its digits add up to 28, which is not a multiple of 3.
What is special about the number 1999?
1999 is a twin prime (1997 and 1999 are both prime); the 303rd prime number.