221

221 is a natural number that lies between 220 and 222. It is the product of two distinct primes, 13 and 17, which makes it a semiprime and an odd composite number. Its divisors are 1, 13, 17, and 221.

In numeral systems, 221 is represented as follows: decimal 221, binary 11011101, octal 335, and hexadecimal DD. In Roman numerals, 221 is written as CXXI. In Unicode and computing terms, the hexadecimal value 0xDD equals 221 in decimal, and the Unicode code point U+00DD corresponds to the Latin capital letter Y with acute (Ý).

In astronomy, 221 Eos is a large main-belt asteroid. It was discovered in 1880 by Johann Palisa and is named after the Greek goddess of the dawn, Eos.

In telecommunications, the country calling code +221 is assigned to Senegal. This code is used for international dialing to telephone numbers within Senegal.

Overall, 221 is notable as a semiprime in mathematics, a standard numeral representation across multiple bases, and as a designation in astronomy and international communications.