I checked this site’s history, and all I found that was about numbers was this post about writing numbers with letters. It includes some stuff about numerology, Greek, the number of the beast, and a party game. Go read it.
But I appear not to have mentioned these more mumdane stylistic niceties about writing numbers:
Write out single-digit numbers, don’t use numerals. Use one, two, et cetera. Not 1, 2, and so on.
Avoid starting sentences with numerals. Rewrite the sentence if possible. Don’t write, “1,223,852 people voted in the election.” Try “More than a million people…” Another example: “Thirty senators agreed.” Not “30 senators…”
In technical material, however, numerals are okay. For example, “Standard voltage for this style of capacitor is 6 volts.” “Don’t allow the motor to exceed 7000 rpm.”
When you refer to something that has a numeral, you may use a numeral: “Repeat Step 4 as often as necessary.”
So there you have it. You can count on me!