Integer

Integer()

Returns: Integer · Updated March 13, 2026 · Core Classes

numbers integers arithmetic precision

The Integer class represents whole numbers in Ruby. In modern Ruby (2.4+), Fixnum and Bignum are unified into just Integer, which automatically handles numbers of any size.

Creating Integers

# Direct literals
42        # => 42
-10       # => -10
0         # => 0
1_000_000 # => 1000000 (underscores allowed)

# Integer() conversion
Integer(3.14)     # => 3 (truncates)
Integer("42")     # => 42
Integer("100", 2) # => 4 (binary)

Integer Methods

# Basic math
42 + 1     # => 43
42 - 1     # => 41
42 * 2     # => 84
42 / 5     # => 8 (integer division)
42 % 5     # => 2 (modulo)
42 ** 2    # => 1764 (exponent)

# Predicates
42.even?   # => true
42.odd?    # => false
42.zero?   # => false
0.zero?    # => true

Bit Operations

# Binary operations
42 & 10    # => 2  (AND)
42 | 10    # => 50 (OR)
42 ^ 10    # => 48 (XOR)
~42        # => -43 (NOT)

# Shifting
42 << 1    # => 84 (left shift)
42 >> 1    # => 21 (right shift)

Integer to Other Types

# To float
42.to_f    # => 42.0

# To string
42.to_s    # => "42"
42.to_s(2) # => "101010" (binary)
42.to_s(16) # => "2a" (hex)

# To rational
42.to_r    # => (42/1)

Iteration

# Upward
5.times { |i| print i }          # => 01234

# Range
(1..5).each { |i| print i }      # => 12345

# Step
(0.step(10, 2)) { |i| print i }  # => 0246810

Practical Examples

Roman Numerals (Custom Implementation)

def to_roman(num)
  return "" if num == 0
  roman_mapping.each do |value, letter|
    return letter * (num / value) + to_roman(num % value) if num >= value
  end
end

roman_mapping = [[1000, "M"], [900, "CM"], [500, "D"], [400, "CD"],
                [100, "C"], [90, "XC"], [50, "L"], [40, "XL"],
                [10, "X"], [9, "IX"], [5, "V"], [4, "IV"], [1, "I"]]

FizzBuzz

(1..15).each do |i|
  result = ""
  result += "Fizz" if i % 3 == 0
  result += "Buzz" if i % 5 == 0
  puts result.empty? ? i : result
end

Bignum (Pre-Ruby 2.4)

# In older Ruby, integers > 2^62-1 were Bignum
# Now automatically handled by Integer
huge = 10**100  # Works fine, no overflow
puts huge.class # => Integer

Constants

Integer::MAX  # Largest integer
Integer::MIN  # Smallest integer

Integers in Ruby are unlimited precision, making them perfect for mathematical calculations without overflow concerns.