Your number is too long for a long integer.
Long Int Range is -2,147,483,648 to 2,147,483,647
Try using Single or Double instead of Long.
Access will still place the # sign after your number but the sign won't be passed to the variable. If you had tried to run your sub it should have given you an Overflow error. This just means the number won't fit inside of your variable.
TIP: If you need to do any maths with very large integers, use the Currency data type. Unlike double and single, currency is fixed-precision, so you can avoid floating-point errors.
Range: -922,337,203,685,477.5808 to 992,337,203,685,477.5807