Count : To count means to find out the number of objects by adding one for every object.

Digit : A digit is a symbol used in the representation of a number.

Divisible : An integer $x$ is called divisible by an integer $y$ if the division $x:y$ has a remainder of zero. For example 4 is divisible by 2 but 5 is not divisible by 2.

Divisible by 4 : An integer $x$ is called divisible by 4 if $x$ is a multiple of 4. An integer is divisible by 4 if and only if the last two digits form a number that is divisible by 4.

Number : A number $x$ is a mathematical symbol representing a quantity.

Expression : An expression is a succession of constants, variables and mathematical operations that if evaluated for specific values of the variables represents a number.