223

223 is a natural number that follows 222 and precedes 224. In mathematics it is classified as a prime number.

As a prime, its only positive divisors are 1 and 223. It is the 48th prime and it is odd. Because 223 ≡ 3 (mod 4), it cannot be written as a sum of two squares.

Numeral representations and encodings of 223 include several common bases and notations. In decimal it is 223; in binary it is 11011111; in octal it is 337; and in hexadecimal it is DF. In Roman numerals it is expressed as CCXXIII. In Unicode, the code point U+00DF corresponds to the Latin small letter sharp S (ß), which has a decimal value of 223.

In science, 223 is the mass number of certain isotopes, notably radium-223. Radium-223 dichloride is used in targeted alpha-particle therapy for cancer under the brand name Xofigo, illustrating a medical application of an isotope with this mass number.