Friday, January 29, 2010
What is so interesting about 13?
- Reverse of the square of 13 is the same as the square of the reverse of 13 i.e. 132= 169; on reversing 169, we get 961 which is the same as the square of reverse of 13 i.e. 312 = 961.
13 x 13 = 169
31 x 31 = 961
- Number 13 is the smallest prime number which can be expressed as the sum of the squares of two prime numbers i.e.
13 = 22 + 32
- From number 13 if we subtract the sum of its digits, we get a perfect square i.e.
13 - (1 + 3) = 9 = 32
13 + (1 x 3) = 16 = 42
- Consider the equations:
132= 169
312= 961
(1+3)2 = 1+6 +9
(3+1)2 = 9 +6+1
- The smallest number whose sum of digits is 13 is a perfect square i.e. 49 = 72 and 4 + 9 = 13.
- The smallest square which contains last three digits alike is 1444. The sum of digits of this number is also 13 i.e.
1+4+ 4+ 4 = 13
- If we place the number 13 before its reverse i.e. 31 we get the number 1331 which is a cubic number i.e. 1331= 113
- If we take the cube of number 13 i.e. 133 = 2197 and rearrange the digits of the cube 2197 we get the famous Ramanujan's number 1729.
- 13 is the average number of the prime factors of the famous Ramanujan's number 1729. i.e.
1729 = 7 x 13 x 19(7 + 13 + 19) ÷ 3 =13
- Take the square of the number 13 i.e. 132 = 169. Now we see that 169 contains many perfect squares in it:
The sum of the digits of the number 169 is a perfect squares and is the square of the sum of the digits of the original number i.e.
1+6+9 = 16 = 42 =(1+3)2
16 + 9 = 25 = 52
16 x 9 = 144 = 122
The number 169 which is perfect square can be expressed as sum of two square i.e.
169 = 132 = 52 + 122
The number 169 can be expressed by number of its two block i.e. 16 and 9 which are perfect squares as follows:
169 = (16 + 9) + (16 x 9)
- Sum of the numbers from 1 to 13 gives 91 which is the smallest number which can be expressed as the sum of two cubes and also as the difference of two cubes i.e.
91 = 33 + 43
91 = 63 - 53
- The reciprocal of number 13 gives
| 1/13 = 0.076923076923076923... |
i.e. the number 076923 repeating indefinitely. This number 76923 is one of the most curious numbers in mathematics.On multiplying the number 76923 by successive multiples of 13, the following beautiful pattern is obtained.
| 76923 | x | 13 | = | 0999999 |
| 76923 | x | 26 | = | 1999998 |
| 76923 | x | 39 | = | 2999997 |
| 76923 | x | 52 | = | 3999996 |
| 76923 | x | 65 | = | 4999995 |
| 76923 | x | 78 | = | 5999994 |
| 76923 | x | 91 | = | 6999993 |
| 76923 | x | 104 | = | 7999992 |
| 76923 | x | 117 | = | 8999991 |
| 76923 | x | 130 | = | 9999990 |
I published the above properties in reference [1] and [2]. Some more fascinating Prime Curios about 13 can be found at PRIME CURIOS.
Some New Fascinating Properties
- The Sum of all Prime Numbers up to 13 is equal to the 13th Prime Number and this is the largest such number.
- The number 13 is a Fibonacci prime, so also the 13th Fibonacci number is Fibonacci Prime and this is also the largest known such number.
- The sum of first 13 Prime numbers is 238, whose sum of digits is 13.
- The number 13 appears for the first time at 111th place in decimal expansion of Pi as shown below:
592307816406286208998628034825342117067982148086513282306647
093844609550582231725359408128481117450284102701938521105559
6446229489549303820......
Interestingly sum of digits of prime factors of 111 ( i.e. 3*37) is 13.
- The concatenation of cubes of numbers from 13 to 1 i.e.
- The only known prime in the Smarandache Mirror sequence i.e.
876543212345678, 98765432123456789,109876543212345678910,
1110987654321234567891011, 12111098765432123456789101112,
131211109876543212345678910111213,
1413121110987654321234567891011121314,.....
is the 13thterm in the sequence.
- A beautiful anagrammatical equation involving 13 is:
- The Smallest composite titanic number whose none of the prime factor is known is 10999 + 13.
- 13 is the Smallest Prime which can be represented as sum of two composite numbers and also sum of two prime numbers in only one way.
- Sum of digits of Smallest 13 digit Prime (i.e. 1000000000039) is equal to 13.
- 31st Prime is preceded by 13 consecutive composite numbers.
- The premier of many countries is designated as PRIME MINISTER containing exactly 13 letters.
- Some other common designations containing 13 letters are CHIEF MINISTER, CHIEF ENGINEER, VICE PRINCIPAL etc.
- Some of the mathematical terms containing 13 letters are PERPENDICULAR, CIRCUMFERENCE, ANTILOGARITHM, APPROXIMATION, QUADRILATERAL and INDETERMINATE.
- The standard length of Broad Gauge Rail in India is 13 meters.
- Teen-hood starts from Thirteen.
- 13 is also called a moon number because the moon moves approx. 13 degrees a day so there are 13 moon months in a year.
- In Japan, the numbers 4 and 9 are considered unlucky, not because 13 can be represented as sum of these two perfect squares but because of their pronunciation. In Japanese, four is pronounced as shi which is the same pronunciation as death. Nine is pronounced ku which has the same pronunciation as torture.
- There is always atleast one friday 13th in each year. In some years, there are two and rarely three. Most recently in 1998 there were three friday 13th. Next such year will be 2009.
Do you believe in GOD?
| An atheist professor of philosophy speaks to his class on the problem science has with God, The Almighty. He asks one of his new students to stand and .....
|
A Dinner with girlfriend
A Dinner with girlfriend a young man goes into a pharmacy and says to the pharmacist
"Hello, could you give me condom ..............
I'm going to my girlfriends for dinner and I think I may be in with a chance!"
The pharmacist gives him the condom and as the young man is going out
He returns and says, "Give me another condom because my girlfriend's sister is very cute too.
She always crosses her legs in a provocative manner when she sees me and I think I might strike it lucky there too."
The pharmacist gives him a second condom and as the boy is leaving he turns back and says "Go on, give me one more condom because my girlfriend's mum is still pretty cute and when she sees me she always makes eyes and since She invited me for dinner I think she is expecting me to make a move!
During dinner, the young man is sitting with his girlfriend on his left,
The sister on his right and the mum facing him.
When the dad gets there, the boy lowers his head and starts praying,
"Dear Lord, bless this dinner and thank you for all you give us".
A minute later the boy is still praying;
"Thank you Lord for your kindness."
Ten minutes go by and the boy is still praying, keeping his head down.
The others look at each other surprised and his girlfriend is even more surprised than the others.
She gets close to the boy and says in his ear, "I didn't know you were so religious."
The boy replies, "I didn't know your dad was a pharmacist!"
Know where you're going in life....
A tourist complimented the local fishermen on the quality of their fish and asked how long it took him to catch them. "Not very long." they answered in unison. "Why didn't you stay out longer and catch more?" The fishermen explained that their small catches were sufficient to meet their needs and those of their families. "But what do you do with the rest of your time?" "We sleep late, fish a little, play with our children, and take siestas with our wives. In the evenings, we go into the village to see our friends, have a few drinks, play the guitar, and sing a few songs. We have a full life." The tourist interrupted, "I have an MBA from Harvard and I can help you! You should start by fishing longer every day. You can then sell the extra fish you catch. With the extra revenue, you can buy a bigger boat." "And after that?" "With the extra money the larger boat will bring, you can buy a second one and a third one and so on until you have an entire fleet of trawlers. Instead of selling your fish to a middle man, you can then negotiate directly with the processing plants and maybe even open your own plant. You can then leave this little village and move to Mexico City , Los Angeles , or even New York City ! From there you can direct your huge new enterprise." "How long would that take?" "Twenty, perhaps twenty-five years." replied the tourist. "And after that?" "Afterwards? Well my friend, that's when it gets really interesting, " answered the tourist, laughing. "When your business gets really big, you can start buying and selling stocks and make millions!" "Millions? Really? And after that?" asked the fishermen. "After that you'll be able to retire, live in a tiny village near the coast, sleep late, play with your children, catch a few fish, take a siesta with your wife and spend your evenings drinking and enjoying your friends." " That's what I am doing now" Replied the fisherman And the moral of this story is: ........ Know where you're going in life.... you may already be there!! |








