542

542 is an even integer. It factors as 2 × 271, with 271 prime, making 542 a semiprime. Its positive divisors are 1, 2, 271, and 542. In common numeral systems, 542 is 1000011110 in binary, 0x21E in hexadecimal, and 1036 in octal. It can also be expressed as 271 + 271, illustrating an instance of an even number as the sum of two primes.

Roman numerals represent 542 as DXLII. It is one more than 541 and one less than 543, and like many other integers, it participates in modular arithmetic and number theory contexts, though it has no widely known special mathematical constants associated with it.

In the calendar, the year 542 CE falls during the early Byzantine period under Justinian I. The Plague of Justinian, which began in 541, continued into 542, causing widespread mortality and disruption across the empire. Other regions at the time had limited, fragmented records, so details vary by source.