Your Social Security number is a powerful string of digits. It's the identification number the government uses to track your wages, and it's something you've probably heard you should keep under wraps to the greatest extent possible. The reason? If your Social Security number falls into the wrong hands, you could wind up a victim of identity theft.

The tricky thing, of course, is that you may land in a host of scenarios where you're asked to provide that number. For example, you'll typically need it to open a bank account, or to enroll in a retirement plan like an IRA. But there are some situations where you may be asked to give out your Social Security number even though you're not required to. Here are a few where it's perfectly OK to say no.

Pile of Social Security cards

IMAGE SOURCE: GETTY IMAGES.

1. When you're applying for a job

Once you're offered a job, you'll need to give out your Social Security number in the course of the onboarding process. This way, your employer can verify your identity for wage-reporting purposes. And you want that to happen, because your Social Security retirement benefits will be based on your lifetime earnings, so any missing wages on your record could cause you to lose out financially later in life.

That said, there's really no need to give out your Social Security number during the job application process. An employer might ask for it to verify that you're eligible to be hired should the desire to make you an offer come to be, but in most cases, providing that number shouldn't be mandatory.

2. When you're signing up for a loyalty program

It's common to be asked to provide your Social Security number when you're applying for a new credit card. But if you're simply applying for a loyalty card -- meaning, one that gives you rewards at a specific retailer based on your spending -- then there's no need to give out that number. The reason? Loyalty cards don't give you any sort of line of credit. They can't be used to borrow money or pay bills, and as such, you really shouldn't have to provide much, if any, personal information to get one.

3. When you're registering a child for school

To enroll your child in public school, you'll generally need to prove that you live where you say you do, and to that end, you'll need to supply documents like utility bills and a driver's license that list your address. Your Social Security number, though, should not be on the list of necessary identification items to supply.

The same holds true when you're applying for college, or when a child of yours is doing the same. The only time your Social Security number will come into play is if you're applying for financial aid, but if you aren't, you shouldn't have to share it.

4. When you're visiting a doctor

This one's a bit of a gray area. It's common for medical offices to ask for your Social Security number, but the reason they do so is to have a means of tracking you down if you fail to make good on an outstanding bill. Much of the time, you don't need to provide a Social Security number to get medical care; providing your insurance information will suffice. This holds true even if you're on Medicare. In fact, Medicare recently replaced its old ID cards, which contained Social Security numbers, with new ones, to protect that very information. If a medical office insists that you must provide a Social Security number, push back. Ask why that number is needed, how it will be used, and what steps will be taken to keep it secure.

5. When a random caller asks for it over the phone

Banks, companies, and government agencies generally won't call you up out of the blue asking for your Social Security number. If you get an unsolicited call and you're asked to provide that information, hang up the phone and do not, under any circumstances, comply. In fact, you should really report the number that called you to the Social Security Administration so that it can investigate and perhaps nip that scam in the bud.

You can't afford to let your Social Security number fall into the wrong hands, so be sure to know when you should and shouldn't give that information out. Furthermore, it's a wise idea to memorize that number and store your Social Security card in a secure place, like a locked safe at home. Carrying that card around at all times only increases your chances of losing it or having it stolen, and since it's not something you should be using on a daily basis, there's no need to expose yourself to that risk.