Under the hood, there are two kinds of integers—small integers, called fixnums, and large integers, called bignums.
The range of values for a fixnum depends on the machine. The minimum range is −536,870,912 to 536,870,911 (30 bits; i.e., −2**29 to 2**29 − 1) but many machines provide a wider range.
Bignums can have arbitrary precision. Operations that overflow a fixnum will return a bignum instead.
All numbers can be compared with eql or =; fixnums can
also be compared with eq. To test whether an integer is a fixnum or a
bignum, you can compare it to most-negative-fixnum and
most-positive-fixnum, or you can use the convenience predicates
fixnump and bignump on any object.
The read syntax for integers is a sequence of (base ten) digits with an optional sign at the beginning and an optional period at the end. The printed representation produced by the Lisp interpreter never has a leading ‘+’ or a final ‘.’.
-1 ; The integer −1. 1 ; The integer 1. 1. ; Also the integer 1. +1 ; Also the integer 1.
See Numbers, for more information.