The number 687
687 is a composite number with 4 divisors. Its prime factorisation is 3 × 229. Divisors (4): 1, 3, 229, 687.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 687: a semiprime: 3 × 229, the product of two primes.
- 2
687 is composite. Its prime factorisation is
- 3
The divisors add up to 920; without 687 itself that is 233, so 687 is deficient (233 is less than 687). Euler's totient φ(687) = 456 numbers up to 687 share no factor with it.
- 4
The digits of 687 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 38 steps to reach 1.
LaTeX source of the formulas on this page
\[ 687 = 3 \times 229 \]
687 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 920 |
| Euler totient φ(n) | 456 |
| Square | 471969 |
| Cube | 324242703 |
| Square root | 26.210685 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 38 |
| Scientific notation | 6.87 × |
687 in other forms
| Form | Value |
|---|---|
| In words | six hundred and eighty-seven |
| Roman numerals | DCLXXXVII |
| Binary (base 2) | 1010101111 |
| Octal (base 8) | 1257 |
| Hexadecimal (base 16) | 2AF |
| Base 3 | 221110 |
| As time | 687 seconds = 11 min 27 s |
Is 687 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 | Yes (687 ÷ 3 = 229) | 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 2) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 7) | 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 | No (remainder 7) | 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 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 687 a prime number?
No. 687 = 3 × 229, so it is divisible by 3.
What are the factors of 687?
1, 3, 229, 687.
What is 687 in binary?
1010101111 (hexadecimal 2AF, octal 1257).
What is the square root of 687?
About 26.2107.
What is 687 in Roman numerals?
DCLXXXVII.
Is 687 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 687?
687 is a semiprime: 3 × 229, the product of two primes.