Characteristics of Seven (7)
1. It is a prime number. Prime number is a number which has only two factors 1 and the number itself.
2. There are seven days in a week. They are – Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday.
3. The oldest puzzle recorded in Ahmes Papyrus has another version like this—
As I was going to St. Ives,
I met a men with 7 wives. Each wife had 7 sacks.
Each sack has 7 cats.
Each cat had 7 kits.
Kits, cats, sack and wives
how many were going to St. Ives?
This puzzle requires the knowledge of Geometric Progression. In simple words, the total number = 1 + 7 + 49 + 343 + 2401 = 2801.
4. Seven (7) is the congruent number because it is the area of the triangle with sides 35/12, 24/5 and 337/60. A triangle is said to be congruent if its area comes out to be an integer.
5. It is a Mersenne Prime number. A prime which can be written as 2n – 1 is said to be Mersenne Prime. 7 = 23 – 1
6. The sevenths power of number 14459929 has a very interesting feature. 7th Power of every digit of 14459929 sums up to 14459929.
14459929 = 17 + 47 + 47 + 57 + 97 + 97 + 27 + 97
7. The factorial of seven (7!) is 5040. This result contains 4 digits with 2 zeros, i.e. 50% zero. Probably it is the unique factorial with this property.
8. No perfect square ends with 7.
9. The smallest positive integer whose reciprocal 1/7 has a pattern of more than one repeating digit. Example:- 1/7 = 0.142857 142857 142857….This number 142857 shows an explicit feature when it is multiplied by 1, 2, 3, 4, 5 and 6. Let’s see it-
142857 x 1 = 142857
142857 x 2 = 285714
142857 x 3 = 428571
142857 x 4 = 571428
142857 x 5 = 714285 142857 x 6 = 857142
Did you notice anything? Yes, the digit of the product comes in a cyclic order and when you prepare a multiplicative table on the basis of the result of the above product the sum of each row and column comes out to be 27.
| Digit | 1 | 4 | 2 | 8 | 5 | 7 | Digit Sum |
| 1 | 1 | 4 | 2 | 8 | 5 | 7 | 27 |
| 2 | 2 | 8 | 5 | 7 | 1 | 4 | 27 |
| 3 | 4 | 2 | 8 | 5 | 7 | 1 | 27 |
| 4 | 5 | 7 | 1 | 4 | 2 | 8 | 27 |
| 5 | 7 | 1 | 4 | 2 | 8 | 5 | 27 |
| 6 | 8 | 5 | 7 | 1 | 4 | 2 | 27 |
| Column sum | 27 | 27 | 27 | 27 | 27 | 27 | |
10. Seven can be portioned in 11 ways.
11. The seven bridges of Konigsberg in Germany gave birth to new branch of Mathematics called Topology. Leonard Euler (1707-1783) solved this problem.
12. No perfect square ends with 7. Any number that ends with 2, 3, 7 or 8 can’t be a perfect square.
13. It is a Lucas Number. 1, 3, 4, 7, 11, 18… are the Lucas number. In Lucas Number, the next number is the sum of previous two.
14. It is the sum of 1st and 3rd factorials. 1! + 3! = 7
15. It is the first centered hexagonal number.
1. There are 7 different ways of linking four hexagons together. One of them is shown here.
2. The opposite side of a die cube sum up to 7.
1. It is the first prime which can be written in the form of 6m + 1, where m is a positive integers.
2. Here is an interesting game based on 7.
7 is a Prime Number
73 is a Prime Number
739 is a Prime Number.
7393 is a Prime Number.
73939 is a Prime Number.
739391 is a Prime Number.
7393913 is a Prime Number.
3. In the Fermat’s Last Theorem xn + yn = zn, for n = 7 this equation has no solution was proved by Lame in 1840.
14. The sum of the squares of the first seven primes was 666, the supposed number of the beast from Revelations.
666=2^2+3^2+5^2+7^2+11^2+13^2+17^2
15. The smallest prime Palindrome number 7778777 has only two digits in it ,i.e 7 and 8.
Send your comments to
Rajesh Kumar Thakur
rkthakur1974@gmail.com
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