Use numerals when writing in such grandiose terms. If you're tempted to use such a large number at the beginning of a sentence, recast the sentence so that it does not begin with the number. In casual expressions, it's all right to omit the numerals. If I've told you once, I've told you a thousand times. Of course, there are hundreds of other special cases and exceptions to the rules I've listed here.
Most people tend to talk louder on a cellular phone, and that can annoy others.
Also, it may embarrass listeners because they may feel they're eavesdropping. Invest in a hands-free device if you must talk on the phone while driving. You may be able to control your vehicle and handle a phone at the same time, but seeing you do it worries other motorists. Heed instructions about using your phone on an aircraft. 1101 King Street, Suite 110, Alexandria, VA 22314.