VeasnaYim, Good evening.
Initially 1717E1 is not a NUMBER.
It can perhaps be a CODE of a product or something else.
1717 is a NUMBER.
CITY is a TEXT.
1717CITY is an ALPHANUMERIC expression, treated inside EXCEL as a TEXT.
1717B4; 1717C2; 1717D. All of these are TEXTs.
On your specific case, 1717E is a TEXT, BUT...1717E3 is not.
EXCEL treat this as a MATH Expression because the "e" or "E".
Then, if after "e"or "E" there is some digit, suppose 3 or 1, the final result will be: TEXT plus zeros.
1717E = 1717E
1717E1 = 17.170
1717E3 = 1.717.000
1717E7 = 17.170.000.000
If you want use this as a code for something, format the cell or cells to TEXT.
After it retype the code.
Please, tell us if it worked for you.
Fell free to ask anything you need.
I hope it helps.