Buying Shares in Round Lots
There are some advantages to buying round lots of shares (multiples of 100 shares), but they don’t apply to everyone. There could be limitations on odd lots (lots that are not multiples of 100)however. The broker might add 1/8 of a point to the price. Some limit orders might not be accepted for odd lots. If these shares cover short calls, you usually need a round lot. If you want to write covered calls, you’ll need a round lot.
Other than that, there’s really nothing special about selling 100 shares, 37 shares or any other number.