5 is the natural number that proceeds 4 and precedes 6.

In mathematics

• It is a Fermat composite number.
• A number is divisible by 5 if the last digit is 0 or 5 in base-10. 
• 5 is also the 4th number in the Fibonacci sequence.
• It is the only known odd untouchable number.
• Base-5 in p-adic is the first base to support imaginary numbers as a real representation, as the base-5 p-adic for -1 (...4444) has a square root.

Geometry

• A five-sided shape is called a pentagon.
• The minimum number of cells (3D boundaries) in a 4-dimensional shape is five.
  • This shape is also one of the six 4-dimensional platonic solids.

Algebra

5 is the value of the central cell of the first non-trivial normal magic square, called the Luoshu square.

Basic calculations

Multiplication

-	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
${\displaystyle 5\times x}$	5	10	15	20	25	30	35	40	45	50	55	60	65	70	75	80	85	90	95	100

Division

-	1	2	3	4	5	6	7	8	9	10
${\displaystyle 5\div x}$	5	2.5	1.66666666667	1.25	1	0.83333333333	0.71428571428	0.625	0.55555555555	0.5
${\displaystyle x\div 5}$	0.2	0.4	0.6	0.8	1	1.2	1.4	1.6	1.8	2

Exponentiation

-	1	2	3	4	5	6	7	8	9	10
5x	5	25	125	625	3,125	15,625	78,125	390,625	1,953,125	9,765,625
x5	1	32	243	1,024		7,776	16,807	32,768	59,049	10,000

Significance

• Humans have 5 fingers.
• Humans have 5 toes.
• Most starfish have 5 legs.
• Blueberries have 5 points.

Bases

5's value is:

• 101 in Binary.
• 12 in Ternary.
• 11 in Quaternary.
• 10 in Quinary.
• 5 in Seximal+