- published: 30 Mar 2016
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30 (thirty) is the natural number following 29 and preceding 31.
30 is the sum of the first four squares, which makes it a square pyramidal number.
It is a primorial and is the smallest Giuga number.
30 is the smallest sphenic number, and the smallest of the form Failed to parse (Missing texvc executable; please see math/README to configure.): 2\cdot 3\cdot r
Thirty has but one number[citation needed] for which it is the aliquot sum: the square number 841.
Adding up some subsets of its divisors (e.g., 5, 10 and 15) gives 30, hence 30 is a semiperfect number.
30 is the largest number such that all coprimes smaller than itself, except for 1, are prime.
A polygon with thirty sides is called a tricontagon.
The icosahedron and the dodecahedron are Platonic solids with 30 edges. The icosidodecahedron is an Archimedean solid with 30 vertices, and the Tutte–Coxeter graph is a symmetric graph with 30 vertices.
E8 has Coxeter number 30.
30 is a Harshad number.
Since any group G such that |G| = pnm, where p does not divide m, has a subgroup of order pn, and 30 is the only number less than 60 that is not either a prime or of the above form, it is the only candidate for the order of a simple group less than 60 that one needs other methods to reject.
A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers.
Mathematical operations are certain procedures that take one or more numbers as input and produce a number as output. Unary operations take a single input number and produce a single output number. For example, the successor operation adds one to an integer, thus the successor of 4 is 5. Binary operations take two input numbers and produce a single output number. Examples of binary operations include addition, subtraction, multiplication, division, and exponentiation. The study of numerical operations is called arithmetic.
A notational symbol that represents a number is called a numeral. In addition to their use in counting and measuring, numerals are often used for labels (telephone numbers), for ordering (serial numbers), and for codes (e.g., ISBNs).