Bignum

From RubySpec

Bignum objects hold integers that are outside Fixnum's range. Bignum objects are automatically created when storing integer calculations in a Fixnum would cause an overflow error. Bignum calculations that would fit in a Fixnum are automatically converted to Fixnum(Programming Ruby, 1st edition). Here are some conceptual examples

 irb(main):001:0> 1000.class
 => Fixnum
 irb(main):002:0> 100.class
 => Fixnum
 irb(main):003:0> (1000*100).class
 => Fixnum
 irb(main):004:0> (1000**100).class
 => Bignum

 irb(main):002:0> (1000**100).class
 => Bignum
 irb(main):003:0> ((1000**100)/(1000**100)).class
 => Fixnum