The number 642
642 is a composite number with 8 divisors. Its prime factorisation is 2 × 3 × 107. Divisors (8): 1, 2, 3, 6, 107, 214, 321, 642.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
642 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
642 is composite. Its prime factorisation is
- 3
The divisors add up to 1296; without 642 itself that is 654, so 642 is abundant (654 is more than 642). Euler's totient φ(642) = 212 numbers up to 642 share no factor with it.
- 4
The digits of 642 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 25 steps to reach 1.
LaTeX source of the formulas on this page
\[ 642 = 2 \times 3 \times 107 \]
642 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 1296 |
| Euler totient φ(n) | 212 |
| Square | 412164 |
| Cube | 264609288 |
| Square root | 25.337719 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 25 |
| Scientific notation | 6.42 × |
642 in other forms
| Form | Value |
|---|---|
| In words | six hundred and forty-two |
| Roman numerals | DCXLII |
| Binary (base 2) | 1010000010 |
| Octal (base 8) | 1202 |
| Hexadecimal (base 16) | 282 |
| Base 3 | 212210 |
| As time | 642 seconds = 10 min 42 s |
Is 642 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (642 ÷ 2 = 321) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (642 ÷ 3 = 214) | 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 | Yes (642 ÷ 6 = 107) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 3) | 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 4) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 642 a prime number?
No. 642 = 2 × 3 × 107, so it is divisible by 2.
What are the factors of 642?
1, 2, 3, 6, 107, 214, 321, 642.
What is 642 in binary?
1010000010 (hexadecimal 282, octal 1202).
What is the square root of 642?
About 25.3377.
What is 642 in Roman numerals?
DCXLII.
Is 642 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 642?
It is a composite number with 8 divisors.