Here’s your problem. There are both letters and numbers in that ID, so it must be created as a string. You’re also missing either let or const in front of the variable definition. I recommend this instead:
const number = "Uf79266972d007f2a3886bf73676860"
Your other example works because it’s a true number and the value for which you’re searching is also a number (even though you’re wrapping it as a string in your filterByFormula formula, Airtable apparently considers them to be equivalent).