Sunday, August 1, 2010

7 | Number Detective . 4




Hey there! I'm Chychy.
Welcome to Number Detective.

My beat is the city streets. The job is to bring you the best numbers we can find out there. Then share all sorts of cool stuff about them with you.


7 is a big number. Not big like large, but you know big like important. 7 days in a week, 7 seas, the 7th inning stretch at a Sox game (hotdog!) and of course 7th grade where I'm at now. I found this 7 in Paisley Park, a really cool street near Fields Corner in Dorchester.

7 always brings a smile to my face. Maybe because it's a happy number. Do you remember about happy numbers from when we found the number 44? You square each digit in the number (multiply it by itself) - for 7 there's just a single digit of course - add them together and repeat the process. In a few steps happy number will soon reduce to 1. An unhappy number will just keep like running around in circles chasing its tail but never reaching 1. Here's how it goes for 7 - and it doesn't even take 7 steps!
7
49 - 7 2 (7x7 = 49)
97 - 4 2 + 9 2 (4x4 + 9x9 = 97)
130 - 9 2 + 7 2 (9x9 + 7x7 = 130)
10 - 1 2 + 3 2 (1x1 + 3x3 = 10)
1 - 1 2 + 0 2 (1x1 + 0x0 = 1)
7 is also a prime number. A prime is any number that can only be evenly divided (with no remainder) by 1 and itself. The first 7 primes are 2, 3, 5, 7, 11, 13 and 17. 1 - because 1 and 'itself' are the same - is not considered a prime. So 7 is a prime because it can only be evenly divided by 1 and 7. This is unlike, say 12, which can be divided by 1, 2, 3, 4, 6 and 12. 12 is like way divisible. No one has ever figured out any pattern in the occurrence of prime numbers. It's a big mystery. But the Number Detective is on it and will get back to you.

Image ... The number 7. Dorchester, Mass.

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