The number 638
638 is a composite number with 8 divisors. Its prime factorisation is 2 × 11 × 29. Divisors (8): 1, 2, 11, 22, 29, 58, 319, 638.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 638: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
638 is composite. Its prime factorisation is
- 3
The divisors add up to 1080; without 638 itself that is 442, so 638 is deficient (442 is less than 638). Euler's totient φ(638) = 280 numbers up to 638 share no factor with it.
- 4
The digits of 638 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 56 steps to reach 1.
LaTeX source of the formulas on this page
\[ 638 = 2 \times 11 \times 29 \]
638 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 1080 |
| Euler totient φ(n) | 280 |
| Square | 407044 |
| Cube | 259694072 |
| Square root | 25.258662 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 56 |
| Scientific notation | 6.38 × |
638 in other forms
| Form | Value |
|---|---|
| In words | six hundred and thirty-eight |
| Roman numerals | DCXXXVIII |
| Binary (base 2) | 1001111110 |
| Octal (base 8) | 1176 |
| Hexadecimal (base 16) | 27E |
| Base 3 | 212122 |
| As time | 638 seconds = 10 min 38 s |
Is 638 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (638 ÷ 2 = 319) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 2) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 8) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (638 ÷ 11 = 58) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 2) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 638 a prime number?
No. 638 = 2 × 11 × 29, so it is divisible by 2.
What are the factors of 638?
1, 2, 11, 22, 29, 58, 319, 638.
What is 638 in binary?
1001111110 (hexadecimal 27E, octal 1176).
What is the square root of 638?
About 25.2587.
What is 638 in Roman numerals?
DCXXXVIII.
Is 638 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 638?
638 is a happy number: repeatedly adding the squares of its digits reaches 1.