Mathematically 72

Seventy Two (72)
1. It is equal to half of the gross.
½ x 144 = 72

2. The sum of first eight even number is 72.
2 + 4 + 6 + 8 +10 + 12 + 14 + 16 = 72

3. It is the only number which is eight times the sum of its own digits.
72 = 8 x (7 + 2)

4. It is the smallest number that can be written as the sum of two prime number in two distinct ways and the most interesting part of this partition is that the primes used ends with 1.
72 = 11 + 61
= 31 + 41

5. The normal human pulse rate is 72 beats/ minutes at rest.

6. An isosceles triangle having a pair of 72 degree angle is called Golden triangle.

7. It is one- fifth of a central angle (360 degree) of circle.

8. The internal angle of a regular pentagon is 72 degree.

9. It is divisible by every number from 1 to 10 apart from 5, 7 and 10.

10. It is the smallest 5th power equal to the sum of 5 other 5th powers.
72^5 = 19^5 + 43^5 + 46^5 + 47^5 + 67^5

11. In financial circle rule of 72 is a simple method to quickly estimate compound interest. If you want to know how long will it take to double your money, divide 72 by the interest rate and the answer will be the number of years.

12. It is the sum of four consecutive primes as well as the sum of six consecutive prime number.
72 = 13 + 17 + 19 + 23 (sum of 4 consecutive numbers)
= 5 + 7 + 11 + 13 + 17 + 19 (sum of 6 consecutive numbers)

13. It is a Harshad number on base 10.

14. The atomic number of Hafnium is 72.

15. It is an Abundant number because the sum of factors of 72 excluding itself is more than 72. The factors are- 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36 and 72.

16. It is a 25- gonal number.

17. It is the maximum number of sphere that can touch another sphere in a lattice packing in 6 dimensions.

18. The great Rhombicuboctahedron in an Archimedean solid is 72 edges.

19. The sum of the eight row of Lozanic triangle is 72.
72 = 1 + 4 + 12 + 19 + 19 + 12 + 4 + 1
The Lozanic triangle is a triangular array of binomial coefficients similar to Pascal’s triangle. It is named after Sima Lozanic, the Serbian chemist.


Dr Rajesh Kumar Thakur
rkthakur1974@gmail.com