The number 842
842 is a composite number with 4 divisors. Its prime factorisation is 2 × 421. Divisors (4): 1, 2, 421, 842.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 842: a semiprime: 2 × 421, the product of two primes.
- 2
842 is composite. Its prime factorisation is
- 3
The divisors add up to 1266; without 842 itself that is 424, so 842 is deficient (424 is less than 842). Euler's totient φ(842) = 420 numbers up to 842 share no factor with it.
- 4
The digits of 842 add up to 14, and repeating that until one digit is left gives the digital root 5. The Collatz sequence (halve if even, else 3n+1) takes 41 steps to reach 1.
LaTeX source of the formulas on this page
\[ 842 = 2 \times 421 \]
842 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 1266 |
| Euler totient φ(n) | 420 |
| Square | 708964 |
| Cube | 596947688 |
| Square root | 29.017236 |
| Digit sum / digital root | 14 / 5 |
| Collatz steps to 1 | 41 |
| Scientific notation | 8.42 × |
842 in other forms
| Form | Value |
|---|---|
| In words | eight hundred and forty-two |
| Roman numerals | DCCCXLII |
| Binary (base 2) | 1101001010 |
| Octal (base 8) | 1512 |
| Hexadecimal (base 16) | 34A |
| Base 3 | 1011012 |
| As time | 842 seconds = 14 min 2 s |
Is 842 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (842 ÷ 2 = 421) | 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 2) | 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 2) | 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 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 5) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 2) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 6) | 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 842 a prime number?
No. 842 = 2 × 421, so it is divisible by 2.
What are the factors of 842?
1, 2, 421, 842.
What is 842 in binary?
1101001010 (hexadecimal 34A, octal 1512).
What is the square root of 842?
About 29.0172.
What is 842 in Roman numerals?
DCCCXLII.
Is 842 divisible by 3?
No. Its digits add up to 14, which is not a multiple of 3.
What is special about the number 842?
842 is a semiprime: 2 × 421, the product of two primes.