Friday 6 September 2024

New Telephone Number


It's always exciting to get a new telephone number because of the properties of the number that may turn up. Having arrived in Australia for a temporary stay, I needed a telephone number and the number that I was given was:$$0451591949 \rightarrow 451591949$$Now this number is prime but has additional "primeness" embedded in it because:$$ \text{Sum of digits is }47 \text{ and prime}\\47 \rightarrow 4 + 7 = 11 \\ 11 \rightarrow 1+1=2 \\ \text{ 2 (the digital root) is prime}$$Now 1949 and 1951 form a pair of twin primes but it turns out that:$$ 451591949 \text{ and } 4511591951 \\ \text{ also form a pair of twin primes}$$Furthermore:$$451591949 \text{ is a Sophie Germain prime} \\ 451591949 \times 2 + 1 = 903183899 \text{ a prime}$$\(451591949\) is also a Chen prime defined as a prime number  \(p\)  such that  \(p+2\)  is either a prime or a semiprime. 
Jing Run Chen, after which they are named, proved in 1966 that there are infinitely many such primes. Binbin Zhou has proved in 2009 that the Chen primes contain arbitrarily long arithmetic progressions.

So overall I'm very happy with my new prime telephone number even though it will lapse and be discarded once I leave the country. For now though it's mine and prime!

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