The number 505
505 is a palindrome: it reads 505 backwards too. Its prime factorisation is 5 × 101. Divisors (4): 1, 5, 101, 505.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 505: a palindrome: it reads 505 backwards too; a semiprime: 5 × 101, the product of two primes.
- 2
505 is composite. Its prime factorisation is
- 3
The divisors add up to 612; without 505 itself that is 107, so 505 is deficient (107 is less than 505). Euler's totient φ(505) = 400 numbers up to 505 share no factor with it.
- 4
The digits of 505 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 61 steps to reach 1.
LaTeX source of the formulas on this page
\[ 505 = 5 \times 101 \]
505 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 612 |
| Euler totient φ(n) | 400 |
| Square | 255025 |
| Cube | 128787625 |
| Square root | 22.472205 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 61 |
| Scientific notation | 5.05 × |
505 in other forms
| Form | Value |
|---|---|
| In words | five hundred and five |
| Roman numerals | DV |
| Binary (base 2) | 111111001 |
| Octal (base 8) | 771 |
| Hexadecimal (base 16) | 1F9 |
| Base 3 | 200201 |
| As time | 505 seconds = 8 min 25 s |
Is 505 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 (505 ÷ 5 = 101) | 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 1) | 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 1) | 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 10) | 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 505 a prime number?
No. 505 = 5 × 101, so it is divisible by 5.
What are the factors of 505?
1, 5, 101, 505.
What is 505 in binary?
111111001 (hexadecimal 1F9, octal 771).
What is the square root of 505?
About 22.4722.
What is 505 in Roman numerals?
DV.
Is 505 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 505?
505 is a palindrome: it reads 505 backwards too; a semiprime: 5 × 101, the product of two primes.