11. 12,345,678,987,654,321 is the product of 111,111,111 x 111,111,111. Notice the sequence of the numbers 1 to 9 and back to 1. 

12. Have you ever noticed that the opposite sides a die always add up to seven (7) 

13. Trigonometry is the study of the relationship between the angles of triangles and their sides 

14. Abacus is considered the origin of the calculator 

15. Here is an interesting trick to check divisibility of any number by number 3.A number is divisible by three if the sum of its digits is divisible by three (3) 

16. Do you know the magic of no. nine (9)? Multiply any number with nine (9 ) and then sum all individual digits of the result (product) to make it single digit, the sum of all these individual digits would always be nine (9). 

17. If you add up the numbers 1-100 consecutively (1+2+3+4+5...) the total is 5050 

18. A 'jiffy' is an actual unit of time for 1/100th of a second 

19. Have you heard about a Palindrome Number? It is a number that reads the same backwards and forward, e.g. 12421 

20. Have you heard about Fibonacci? It is the sequence of numbers wherein a number is the result of adding the two numbers before it! Here is an example: 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on