The number 2005
2005 is a composite number with 4 divisors. Its prime factorisation is 5 × 401. Divisors (4): 1, 5, 401, 2005.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 2005: a semiprime: 5 × 401, the product of two primes.
- 2
2005 is composite. Its prime factorisation is
- 3
The divisors add up to 2412; without 2005 itself that is 407, so 2005 is deficient (407 is less than 2005). Euler's totient φ(2005) = 1600 numbers up to 2005 share no factor with it.
- 4
The digits of 2005 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 112 steps to reach 1.
LaTeX source of the formulas on this page
\[ 2005 = 5 \times 401 \]
2005 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 2412 |
| Euler totient φ(n) | 1600 |
| Square | 4020025 |
| Cube | 8060150125 |
| Square root | 44.777226 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 112 |
| Scientific notation | 2.005 × |
2005 in other forms
| Form | Value |
|---|---|
| In words | two thousand and five |
| Roman numerals | MMV |
| Binary (base 2) | 11111010101 |
| Octal (base 8) | 3725 |
| Hexadecimal (base 16) | 7D5 |
| Base 3 | 2202021 |
| As time | 2005 seconds = 33 min 25 s |
Is 2005 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (2005 ÷ 5 = 401) | 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 3) | 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 5) | 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 | No (remainder 5) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 2005 a prime number?
No. 2005 = 5 × 401, so it is divisible by 5.
What are the factors of 2005?
1, 5, 401, 2005.
What is 2005 in binary?
11111010101 (hexadecimal 7D5, octal 3725).
What is the square root of 2005?
About 44.7772.
What is 2005 in Roman numerals?
MMV.
Is 2005 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 2005?
2005 is a semiprime: 5 × 401, the product of two primes.