How to generate random 64-bit unsigned integer in C

I need generate random 64-bit unsigned integers using C. I mean, the range should be 0 to 18446744073709551615. RAND_MAX is 1073741823.

I found some solutions but they concatenates some rand() results or making some incremental arithmetic operations. So results are always 18 digits or 20 digits. I also want outcomes like 5, 11, 33387 not just 3771778641802345472

By the way, I really don't have so much experience with the C but any approach, code samples and idea could be beneficial.