Is 2011 a prime number? It is not obvious as there is no easy formula to test it. Since 2011 is not a large number, the Eratosthenes Sieve Method can be used. But the faster way to know is table look up. Since a table of prime numbers up to 10,000 already exists. The answer is Yes, 2011 is a Prime number. Now the question, why bother with the prime number? What is the use of it? Prime number used to be a subject of curiosity in the Number Theory. You don’t usually ask the use or application of the subject when you sit in the class of math. However, we know at least one use of the prime number in finding HCF & LCM of two numbers. We learned in the primary school, what is the HCF & LCM of 72 & 45? We factor them first into several prime numbers & find the answer.
When I was a kid, I liked cicada very much. I lived in the area which had a lot of tress & open area. During the summer, it was my busy season. The singings of the cicada were everywhere. I was fascinated on the loud audio level with their tiny body. Some of them were green, some were red, some were in between & some were black & bigger. I tried various ways to catch them but not very successful. Eventually I dwelled in the state of enjoy their singings all day long.
Several years ago, I heard the news that in the East Coast, some cicada emerged in huge number and the cycle is 13 or 17 years. Of course we see cicada every year as some of them are not synchronous or cyclical. But these two species are something special because of their huge number when they emerge from the ground. One explanation is that the Mother Nature constantly does the experiment & finds the formula: Prime Number. By mutation, some cicadas hit that number & survive easily. The theory is that most life cycle of predators is 2,3,4 or 5 years. If they hit the same year as our cicada, they eat a lot of cicadas but will miss the cicada in the next cycle when cicadas emerge because 13 and 17 are prime number. In other words, the LCM is a large number. The whole thing is very interesting. If this theory & explanation hold true, the cicadas survive and multiply in large quantity not because they are smart, but because of the Evolution by Mother Nature. Since the evolution is a long time process, we may say that “Time will eventually heal the wounds & solve all the problems”.
PS: I went to Kaiser for physical checkup on January 11. When I got out around eleven o'clock & passed by the register desk, I saw the digital clock on the wall showing 01 11 11, 11 11 11. In other words, I got eleven "1" time wise. So I hit eleven 1 in total. You have to wait until November 11 to supersede this.
