# Versions of Pandas >= 1.3.0:
writer = pd.ExcelWriter('output.xlsx',
                        engine='xlsxwriter',
                        engine_kwargs={'options': {'strings_to_numbers': True}})

# Versions of Pandas < 1.3.0:
writer = pd.ExcelWriter('output.xlsx',
                        engine='xlsxwriter',
                        options={'strings_to_numbers': True})