The number 2
2 is a highly composite number: it has 2 divisors, more than any smaller number, 2! (2 factorial) and the 1st prime number. Its only divisors are 1 and 2.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 2: a highly composite number: it has 2 divisors, more than any smaller number; 2! (2 factorial); the 1st prime number.
- 2
2 is prime, so its only factors are 1 and 2. It is the 1st prime; the next prime is 3.
- 3
The divisors add up to 3; without 2 itself that is 1, so 2 is deficient (1 is less than 2). Euler's totient φ(2) = 1 numbers up to 2 share no factor with it.
- 4
The digits of 2 add up to 2, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 1 steps to reach 1.
2 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 3 |
| Euler totient φ(n) | 1 |
| Square | 4 |
| Cube | 8 |
| Square root | 1.414214 |
| Digit sum / digital root | 2 / 2 |
| Collatz steps to 1 | 1 |
| Scientific notation | 2 × |
2 in other forms
| Form | Value |
|---|---|
| In words | two |
| Roman numerals | II |
| Binary (base 2) | 10 |
| Octal (base 8) | 2 |
| Hexadecimal (base 16) | 2 |
| Base 3 | 2 |
| As time | 2 seconds |
Is 2 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (2 ÷ 2 = 1) | 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 2) | 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 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 2 a prime number?
Yes. 2 is divisible only by 1 and itself.
What are the factors of 2?
1, 2.
What is 2 in binary?
10 (hexadecimal 2, octal 2).
What is the square root of 2?
About 1.4142.
What is 2 in Roman numerals?
II.
Is 2 divisible by 3?
No. Its digits add up to 2, which is not a multiple of 3.
What is special about the number 2?
2 is a highly composite number: it has 2 divisors, more than any smaller number; 2! (2 factorial); the 1st prime number.