[Tex/LaTex] Getting undefined control sequence on anything between “$”

Question

Ive worked with Overleaf before and this is the first time ive come accross this error. Ive added as many packages as i could think of. but everytime i try to use a math symbol it throws this error. Thanks in advance!

"Undefined control sequence.
\N

l.21 \item 123456 $\N
$ "
My Code

    \documentclass{article}

    \usepackage[utf8]{inputenc}
    \usepackage[T1]{fontenc}
    \usepackage[english]{babel}
    \usepackage{textcomp}
    \usepackage{amsthm}
    \usepackage{amsmath}
    \usepackage{amssymb}

    \title{MATH 220 - HW 1}
    \author{}
    \date{}

    \begin{document}

        \maketitle

        \section*{1.2}
            \begin{enumerate}
        \item 123456 $\N$
            \end{enumerate}

     \end{document}

Answer 1

You should define the command, ie \newcommand{\N}{\mathbb}{N}

   \documentclass{article}

    \usepackage[utf8]{inputenc}
    \usepackage[T1]{fontenc}
    \usepackage[english]{babel}
    \usepackage{textcomp}
    \usepackage{amsthm}
    \usepackage{amsmath}
    \usepackage{amssymb}
\newcommand{\N}{\mathbb{N}}
    \title{MATH 220 - HW 1}
    \author{}
    \date{}

    \begin{document}

        \maketitle

        \section*{1.2}
            \begin{enumerate}
        \item 123456 $\N$
            \end{enumerate}

     \end{document}

which outputs