WVGSA Grade 4 Operations and Algebraic Thinking. Practice it free.

The sum of the digits of $27$ is $2 + 7 = 9\textsf{,}$ and $9$ is divisible by $3\textsf{,}$ so $27$ is divisible by $3\textsf{.}$

Five $6\text{s}$ make $30$: $6\textsf{,}$ $12\textsf{,}$ $18\textsf{,}$ $24\textsf{,}$ $30\textsf{.}$

$37$ has only two factors, $1$ and $37$, so it is prime.

The last digit of $45$ is $5\textsf{,}$ so $45$ is divisible by $5\textsf{.}$

Two $3\text{s}$ make $6$: $3\textsf{,}$ $6\textsf{.}$

The smallest prime number is $2$.

The sum of the digits of $81$ is $8 + 1 = 9\textsf{,}$ and $9$ is divisible by $9\textsf{,}$ so $81$ is divisible by $9\textsf{.}$

Two $7\text{s}$ make $14$: $7\textsf{,}$ $14\textsf{.}$