Forty-seven years ago today, my mother Anne, my father Vladimir, my brother Sasha, and I arrived in the United States from what was then the Soviet Union (by way of Austria and Italy, where we waited for our visas to come through). Many, many thanks, America!

Why note this on the 47th anniversary, you might ask? A few years ago, a friend of mine announced that she was going to be specially celebrating not her round-number birthdays, but her prime ones. After all, we view 40 and 50 and the like as round numbers just because of the sheer biological accident that we have five fingers on each hand. If we had had six, 48 and 54 would have been round, and 40 and 50 wouldn’t be. (To be sure, we’d probably be writing 48 and 54 as “40” and “46,” but that’s a separate matter.)

But prime numbers are prime all the universe over, regardless of how many fingers or whatever else a math-using creature might have. And of course we’re in for a prime number drought between 47 and 53, so 47 is worth noting.

This having been said, I reserve the right to post something for the 50th anniversary as well.