What makes this number unique: 8,549,176,320?

How can you leave a room with two legs and return with six legs?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

I am the largest in my family of fifty.
The youngest of our family lives separately from the rest of the family and so do I.
I am regarded as harsh and tough.
I am so large, you cut me in two equal halves,
each half would still be larger than the second largest member of the family.
Who am I?

What does this rebus mean?

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TIME

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

How is the moon similar to a dollar?

What is the word or phrase?