What is the smallest 1-digit composite number?
Referring to only positive integers, the smallest composite number is 4 (2 x 2). A composite number is any number that is the product of two or more prime numbers.*Referring to all integers, it would be the negative number -9, (3 x -3), which is the also the arithmetically lowest one-digit number. However, under normal definitions, negative numbers are not considered prime or composite numbers.