### Basics:

- Ruby has two categories of numbers - integers and floating-point (also called floats).
- Integers are whole numbers that can be positive or negative but cannot be fractions.
- Depending on their size, integers can have the class
`Fixnum`

or`Bignum`

. - Floats are numbers with a decimal place.

## Examples:

```
x = 5.5
x.class
# returns
Float
x = 5
x.class
# returns
Fixnum
x = 11122233344455566677
x.class
# returns
Bignum # basically, Bignum is a very large number
# <a href='http://ruby-doc.org/core-2.0.0/Bignum.html' target='_blank' rel='nofollow'>read this article for more info</a>
```

In Ruby there are a variety of build in methods you can perform on numbers.

## Even:

- Use
`.even?`

to check whether or not an integer is even.

```
15.even?
4.even?
# returns:
false
true
```

## Odd:

- Use
`.odd?`

to check whether or not an integer is odd.

```
15.odd?
4.odd?
# returns:
true
false
```

## Ceil:

- The
`.ceil`

method rounds up to the nearest integers.

```
8.3.ceil
6.7.ceil
# returns:
9
7
```

## Floor:

- The
`.floor`

method rounds down to the nearest integers.

```
8.3.floor
6.7.floor
# returns:
8
6
```

## Next:

- Use
`.next`

to return the next consecutive integer.

```
15.next
2.next
-4.next
# returns:
16
3
-3
```

## To String:

- The
`.to_s`

method changes an integer into a string.

```
15.to_s
# returns:
"15"
```

## Greatest Common Denominator:

- The
`.gcd`

method returns the greatest common denominator of two numbers.

```
15.gcd(5)
9.gcd(4)
# returns:
5
1
```