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real numbers
all possible values, ranging from negative infinity to positive infinity. real numbers can be expressed as decimal numbers, fractions, or even irrational numbers such as the square root of 2 or pi.
you may see the symbol ℝ used to denote real numbers,
integers
all whole numbers, they can be positive, negative or zero
you may see the symbol ℤ used to denote integers
natural numbers
natural numbers are the set of all positive integers.
you may see the symbol ℕ used to denote natural numbers
rational number
a number that can be written as a fraction in its simplest form. it must be possible to write in the form a over b, where a and b are both whole numbers.
this includes all terminating and recurring decimals
factor
a number that divides into another number exactly. for example, the factors of 18 are 1, 2, 3, 6, 9, and 18.
every number has at least two factors, itself and 1
prime numbers
an integer that is greater than 1 that cannot be exactly divided by any whole number other than itself and 1
eg) 2,3,5,7,11
square number
numbers that can be made by multiplying an integer by itself
irrational numbers
real numbers that cannot be represented as simple fractions
eg) pi, numbers with endless non repeating digits after the decimal point
Note 
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