Divisibility Rules (1, 2, 3, 4)

All integers are divisible by $1$.
An integer is divisible by $2$ if it is even -- if it ends in $0$, $2$, $4$, $6$, or $8$.
An integer is divisible by $3$ if the sum of the digits in that integer is also divisible by $3$.
- For example, $816$ is divisible by $3$ because $8+1+6=15$, a number divisible by $3$.
An integer is divisible by $4$ if the last two digits in that integer are also divisible by $4$.
- For example $56$,$234$,$332$ is divisible by $4$ because $32$ is divisible by $4$.
- Note that if the last two digits are $00$, the entire number is divisible by $4$ because $00$ is divisible by $4$.