# Equal+in+number

111

**19 (number)**— ← 18 20 → 19 ← 10 11 12 13 14 15 16 17 …112

**Congruent number**— In mathematics, a congruent number is a positive integer that is the area of a right triangle with three rational number sides.[1] A more general definition includes all positive rational numbers with this property.[2] The sequence of integer… …113

**Real number**— For the real numbers used in descriptive set theory, see Baire space (set theory). For the computing datatype, see Floating point number. A symbol of the set of real numbers …114

**Semiperfect number**— In mathematics, a semiperfect number or pseudoperfect number is a natural number n that is equal to the sum of all or some of its proper divisors.The first few semiperfect numbers are:6, 12, 18, 20, 24, 28, 30, 36, 40, ... OEIS|id=A005835;every… …115

**31 (number)**— ← 30 32 → 31 ← 30 31 32 33 34 35 36 …116

**666 (number)**— For the year 666 AD, see 666. List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 → 666 Cardinal Six hundred …117

**Happy number**— A happy number is defined by the following process. Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a… …118

**Regular number**— The numbers that evenly divide the powers of 60 arise in several areas of mathematics and its applications, and have different names coming from these different areas of study. As an example, 602 = 3600 = 48 times; 75, so both 48 and 75 are… …119

**List of number-one singles from the 1950s (UK)**— This is a list of the number one singles on the UK Singles Chart, during the 1950s. The source for this decade is the New Musical Express chart. =1952= 1 Al Martino Here In My Heart #:November 14 for 9 weeks =1953= 1 Jo Stafford with Paul Weston… …120

**Amicable number**— Amicable numbers are two different numbers so related that the sum of the proper divisors of the one is equal to the other, one being considered as a proper divisor but not the number itself. Such a pair is (220, 284); for the proper divisors of… …