#separator:tab #html:false #tags column:4 Natural (counting) numbers 1, 2, 3, 4, ... math-number-types Whole numbers 0, 1, 2, 3, ... math-number-types Integers ..., −3, −2, −1, 0, 1, 2, 3, ... math-number-types Rational numbers Numbers that can be written as a fraction of two integers math-number-types Irrational numbers Numbers that cannot be written as a fraction math-number-types Real numbers All rational and irrational numbers math-number-types Imaginary numbers Multiples of i, where i² = −1 math-number-types Complex numbers Numbers of the form a + bi math-number-types Even numbers Whole numbers divisible by 2 math-number-types Odd numbers Whole numbers not divisible by 2 math-number-types Prime numbers Numbers above 1 with exactly two factors math-number-types Composite numbers Numbers above 1 that are not prime math-number-types Square numbers 1, 4, 9, 16, 25, ... math-number-types Cube numbers 1, 8, 27, 64, 125, ... math-number-types Triangular numbers 1, 3, 6, 10, 15, 21, ... math-number-types Fibonacci numbers 1, 1, 2, 3, 5, 8, 13, 21, ... math-number-types Perfect numbers Numbers equal to the sum of their proper factors: 6, 28, 496 math-number-types Is 6 perfect? Yes: 1 + 2 + 3 = 6 math-number-types Is 28 perfect? Yes: 1 + 2 + 4 + 7 + 14 = 28 math-number-types Palindromic number A number that reads the same backward and forward (121) math-number-types Twin primes Primes that differ by 2 (11 and 13) math-number-types Mersenne prime A prime of the form 2ⁿ − 1 (7, 31, 127) math-number-types Pi is rational or irrational? Irrational math-number-types √2 is rational or irrational? Irrational math-number-types √9 is rational or irrational? Rational (it equals 3) math-number-types 0.5 is rational or irrational? Rational math-number-types 0.333... is rational or irrational? Rational (1/3) math-number-types Is e rational or irrational? Irrational math-number-types Is zero positive or negative? Neither math-number-types Is zero even? Yes math-number-types Is 1 prime? No math-number-types Is 0 an integer? Yes math-number-types Is −4 a whole number? No math-number-types Is −4 an integer? Yes math-number-types Is 3/4 an integer? No, it is rational math-number-types Is every integer a rational number? Yes (n = n/1) math-number-types Is every rational number an integer? No math-number-types Is every real number rational? No math-number-types Ordinal numbers First, second, third: tell position math-number-types Cardinal numbers One, two, three: tell how many math-number-types Nominal numbers Numbers used as names or labels, like a jersey number math-number-types Opposite of 7 −7 math-number-types Reciprocal of 7 1/7 math-number-types Absolute value of −7 7 math-number-types Negative of a negative A positive: −(−7) = 7 math-number-types Googol 10^100 math-number-types Googolplex 10 to the power of a googol math-number-types Infinity Not a number; the idea of going on without end math-number-types Golden ratio About 1.618, an irrational number: (1 + √5)/2 math-number-types