List of Some Interesting Numbers

 Dear Friends ---

Numbers are very fascinating. Every number is unique and I have written the properties of number 1 - 100 in my blog highlighting some of their characteristics. 

I have been very interested in collecting the name of some of the numbers alphabetically and the list is yet incomplete. Please find the name of some of the numbers I have collected from different sources --

 

1.   Abundant Number

2.   Achilles Number

3.   Admirable Number

4.   Alternating Number

5.   Amenable Number

6.   Amicable Number

7.   Anti- Perfect Number

8.   Apocalyptic Number

9.   Astonishing Number

10.                Automorphic Number

11.                Beast Number

12.                Bell Number

13.                Binomial Number

14.                Cake Number

15.                Cube Number

16.                Catalan Number

17.                Cardinal Number

18.                Composite Number

19.                Congruent Number

20.                Cullen Number

21.                Cyclic Number

22.                Deficient Number

23.                Deceptive Number

24.                Decagonal Number

25.                Economical Number

26.                Esthetic Number

27.                Eulerian Number

28.                Evil Number

29.                Even number

30.                Factorial Number

31.                Fibonacci Number

32.                Friedman Number

33.                Gilda Number

34.                Happy Number

35.                Harmonic Number

36.                Harshad Number

37.                Heptagonal number

38.                Hex number

39.                Hexagonal number

40.                Highly composite number

41.                Hoax number

42.                Hungry number

43.                Impolite number

44.                Inconsummate number

45.                Irrational number

46.                Junctioin number

47.                Kaprekar number

48.                Lehmer number

49.                Leyland number

50.                Lonely number

51.                Lucas number

52.                Lucky number

53.                Magic number

54.                Modest number

55.                Motzkin number

56.                Narcissistic number

57.                Natural number

58.                Nonagonal number

59.                Nude number

60.                Octagonal number

61.                Odd number

62.                Ormiston number

63.                Palindrome number

64.                Pancake number

65.                Pandigital number

66.                Partition number

67.                Pentagonal number

68.                Perfect number

69.                Perrin number

70.                Persistent number

71.                Palindrome number

72.                Practical number

73.                Prime number

74.                Primorial number

75.                Pseudo perfect number

76.                Rare number

77.                Rational number

78.                Real number

79.                Repdigit number

80.                Sastry number

81.                Self number

82.                Semi prime number

83.                Sliding number

84.                Smith number

85.                Sophie German number

86.                Square number

87.                Taxi cab number

88.                Tetrahedral number

89.                Tetranacci number

90.                Transcendental number

91.                Triangular number

92.                Tribonacci number

93.                Twin prime number

94.                Uban number

95.                Ulam number

96.                Untouchable number

97.                Vampire number

98.                Wasteful number

99.                Weird number

100.            Woodall number

101.            Zeisel number

102.            Zuckerman number

 

I do promise that I will start writing about all these numbers in coming days but that needs your support. 

Regards 

 Dr Rajesh Kumar Thakur

 

 

FRIENDLY NUMBER

                                                                      FRIENDLY NUMBERS

FRIENDLY NUMBER is different from Friend / Amicable Numbers. So don't get confused with its similarity.

Friendly Number

Two or more natural numbers are called friendly numbers if they have common abundancy index. The common abundancy index is decided by dividing the sum of all divisors of a number including itself by the number itself.

Example:- 30 has the divisors – 1, 2, 3, 5, 6, 10, 15 and 30

The sum of divisors = 1 + 2 + 3 + 5 + 6 + 10 + 15 + 30 = 72

Abundancy index = 72/30 = 12/5

The abundancy index of a number could be a natural number or rational number.

If the sum of divisors of a number  (excluding itself) = Number itself , it is called Perfect Number

If the sum of divisors of a number  (excluding itself) >Number itself , it is called Abundant Number

If the sum of divisors of a number  (excluding itself) < Number itself , it is called Deficient Number

6 and 28 are Perfect Numbers

Divisor of 6 = 1, 2 and 3 . Sum of divisors = 1 + 2 + 3 = 6

Divisors of 28 are = 1, 2, 4 ,7 and 14 . Sum of divisors = 1 + 2 + 4 + 7 + 14 = 28

6 and 28 are friendly number with abundancy index 2, i.e. any number with abundancy index 2 is called Friendly numbers.

Divisors of 6 = 1, 2, 3 and 6

Sum of Divisors = 1 + 2 + 3 + 6 = 12

Abundancy Index = 12 /6 = 2

Divisor of 28 = 1, 2, 4, 7, 14 and 28

Sum of divisors = 1 + 2 + 4 + 7 + 14 + 28 = 56

Abundancy Index = 56 / 28 = 2

Since 6 and 28 have same abundancy index so they are FRIENDLY NUMBERS.

More examples of friendly numbers are --- (30,140) (2480, 6200 and 40640)

 If you want to know about Amicable/Friends Number 

FRIEND NUMBER/ AMICABLE NUMBERS

READ ANOTHER ARTICLE 

Numbers with Cool Names: Amicable, Sociable, Friendly – TOM ROCKS MATHS

LIST OF DIFFERENT NUMBERS

Do write your comment in comment box.

DR RAJESH KUMAR THAKUR