217 (two hundred ndseventeen) is the

natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called ''Cardinal n ...

following

216 __NOTOC__ Year 216 (Roman numerals, CCXVI) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Sabinus and Anullinus (or, less frequently, ...

and preceding

218 Year 218 (Roman numerals, CCXVIII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Severus and Adventus (or, less frequently, year ...

In mathematics

217 is a

centered hexagonal number In mathematics and combinatorics, a centered hexagonal number, or hex number, is a centered figurate number that represents a hexagon with a dot in the center and all other dots surrounding the center dot in a hexagonal lattice. The following ...

, a 12-gonal number, a centered 36-gonal number, a Fermat pseudoprime to base 5, and a Blum integer. It is both the sum of two positive cubes and the difference of two positive consecutive cubes in exactly one way:

217 = 6^3 + 1^3 = 9^3 - 8^3

. When written in binary, it is a non-repetitive Kaprekar number.The non-repetitive Kaprekar binary numbers in decimal
OEIS It is also the sum of all the

divisor In mathematics, a divisor of an integer n, also called a factor of n, is an integer m that may be multiplied by some integer to produce n. In this case, one also says that n is a multiple of m. An integer n is divisible or evenly divisible by ...

s of .

References

{{Integers, 2 Integers ca:Nombre 210#Nombres del 211 al 219

In mathematics

See also

References