The number 398
398 is a composite number with 4 divisors. Its prime factorisation is 2 × 199. Divisors (4): 1, 2, 199, 398.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 398: a semiprime: 2 × 199, the product of two primes.
- 2
398 is composite. Its prime factorisation is
- 3
The divisors add up to 600; without 398 itself that is 202, so 398 is deficient (202 is less than 398). Euler's totient φ(398) = 198 numbers up to 398 share no factor with it.
- 4
The digits of 398 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 120 steps to reach 1.
LaTeX source of the formulas on this page
\[ 398 = 2 \times 199 \]
398 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 600 |
| Euler totient φ(n) | 198 |
| Square | 158404 |
| Cube | 63044792 |
| Square root | 19.949937 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 120 |
| Scientific notation | 3.98 × |
398 in other forms
| Form | Value |
|---|---|
| In words | three hundred and ninety-eight |
| Roman numerals | CCCXCVIII |
| Binary (base 2) | 110001110 |
| Octal (base 8) | 616 |
| Hexadecimal (base 16) | 18E |
| Base 3 | 112202 |
| As time | 398 seconds = 6 min 38 s |
Is 398 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (398 ÷ 2 = 199) | 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 6) | 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 2) | 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 | No (remainder 2) | 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 398 a prime number?
No. 398 = 2 × 199, so it is divisible by 2.
What are the factors of 398?
1, 2, 199, 398.
What is 398 in binary?
110001110 (hexadecimal 18E, octal 616).
What is the square root of 398?
About 19.9499.
What is 398 in Roman numerals?
CCCXCVIII.
Is 398 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 398?
398 is a semiprime: 2 × 199, the product of two primes.