**NORMAL **- Line perpendicular to a curve or surface.

**CIENTIFIC NOTATION **- Way of displaying numbers either too small or too large. It consists of presenting these numbers as a product of a number from 1 to 10 by a base 10 power. Examples: 47,300 = 4.73 x 10^{4}; 0.000000021 = 2.1 x 10^{-8}.

**NUMBER - **Indicates the number of parts taken into account with the whole. In the fraction is the number that is on top. It is the number that is divided by the number below. In fraction 3/4 the numerator is number 3.

**NUMBER - **A symbol that represents a quantity, a quantity, a position, a measure. The symbols used may be digits (26), letters (twenty six) or others (1A), the latter being a mixture of letters and numbers and corresponding to number 26 in the hexadecimal base.

**RANDOM NUMBER - **Number chosen at random.

**FRIENDLY NUMBER** - Friendly number is a pair of numbers where one of them is the sum of the dividers of the other. As an example, the dividers of 220 are: 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110 whose sum is 284. On the other hand, the dividers of 284 are: 1, 2, 4 , 71 and 142 and their sum is 220. Fermat also discovered par 17,296 and 18,416. Descartes discovered pair 9,363,584 and 9,437,056.

**UP NUMBER** - A natural number is called an ascending number if each of its digits is strictly larger than any of the digits placed on its left. For example, the number 3589.

**CAPICUA NUMBER **- A number is capitalized when read from left to right or right to left always represents the same value, such as 77, 434, 6446, and 82328. To get one number from another, the order is reversed. of the digits and sum with the given number a number of times until a capicua number is found.

**CARDINAL NUMBER** - Is the number of elements in a set. The characteristic associated with the cardinal number is the *cardinality*.

**CYCLIC NUMBER** - Cyclic are numbers that multiplied by another value less than or equal to the number of digits he has, his numbers are repeated cyclically, passing to the end those in front. For example, the first cyclic number is 142857.

**COMPOUND NUMBER** **-** It is a number that has more than two distinct natural dividers, such as 4, 6, 12, 15, 49.

**DECIMAL NUMBER** - Number in which the integer part is separated from the decimal part by a comma.

**EULER NUMBER - **Irrational number, base value of natural logarithms. Its value is calculated by _{}

**MERSENNE NUMBER** - are integers of the form M_{P }= 2^{P} -1. Without_{P} is a prime number, the number **P** It is also. Only 33 Mersenne numbers are known. The last finding corresponds to p = 859 433, whose Mersenne number is 2^{859433} - 1. It is not known if there are an infinite number of them.

**GOLD NUMBER - **The gold number is no more than a numerical value whose approximate value is 1.618. This irrational number _{} It is considered by many to be the symbol of harmony.

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