## A Perfect Day

My sons have a cool birthday: May 2, 2007. It can be written as 5/2/07, and of course 5 + 2 = 7. It’s good that it has such a memorable pattern, because I’m terrible with dates. My wife will surely divorce me if I misstate the date of our anniversary one more time.

But I’m very jealous of my friend Dave, whose son was born three years ago today. How cool is it that his birthday is 6/28?

For those of you who don’t understand why I think that’s cool, consider this: the proper factors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6; likewise, the proper factors of 28 are 1, 2, 4, 7, and 14, and 1 + 2 + 4 + 7 + 14 = 28. These numbers are called perfect numbers for this very reason — the sum of the proper factors is equal to the number itself.

Seventeen asked 6 and 28, “Don’t you two ever do anything wrong?”
“Nope,” they said. “We’re perfect!”

My love is mathematics, but my addiction is ultimate frisbee. I’ve played for 17 years, and my uniform number has always been 28.

A few years ago, I joined a new team, and the captain of the team asked us to email him our request for uniform numbers. Of course, I emailed and asked for 28.

He responded a few minutes later to say that 28 was his number, and I’d have to choose another.

I was dismayed, but I had a back-up plan. I emailed back and requested 6.

He responded again, saying that 6 was taken, too. Egads!

That weekend, we had our first tournament. I noticed that my teammate James was wearing number 6.

I walked over to him and asked casually, “Why did you choose 6 as your uniform number?”

I’m not sure why I asked, or what answer I expected. But his response was the greatest sentence ever spoken to me.

“Because 28 was already taken,” he said.

I didn’t like that I was relegated to my third choice for uniform number, but somehow his response made it all seem okay.

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• 1. John Darrow  |  July 1, 2010 at 10:35 am

So did you end up with 496 as your third choice? 😉

• 2. venneblock  |  July 2, 2010 at 9:06 pm

Oh, if only uniform numbers could have three digits! Though if we’re not constrained by number of digits, I probably would have chosen 2,658,455,991,569,831,744,654,692,615,953,842,176 — I love that it has 37 digits, and each of the digits 1-9 appers at least twice, yet there is no 0.

• […] Bogomolny is hosting the Math Teachers at Play Blog Carnival 28. I’m very excited, since 28 is my favorite number, and I absolutely love the autostereogram that he created to introduce the […]

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