Social security auxiliary pay dependent

Hi all, need some help. For starters, I woke up with 24k pending in my account. My father is owed SSDI for 2 years, along with myself for being a minor at the time. The money was an auxiliary backpay lumpsome. I am still in shock and will call Monday to be sure this is not a typo since this is a crazy amount of money for someone my age. My questions are:

If the 24k is legit, my husband and I’d combined income is above 31k yearly. Is this money taxable? And if so how much will I owe on this? I plan to see a CPA but don’t want to be blind sighted. We make less than 60k yearly combined.

What are the chances of this lumpsome being faulty resulting in me having to pay the money back? On the phone I swear I was told my amount would be 2k. Additionally, my high school filled out paperwork, and I had a phone interview. My father has also already received his backpay.

Any help is appreciated! This is killing me! I’m excited to have the money but can’t help but to be inquisitive it