142

142 is a natural number that comes after 141 and before 143. In mathematics, it is classified as an even composite number. Its prime factorization is 2 × 71, with 71 prime, making 142 a semiprime. The divisors of 142 are 1, 2, 71, and 142. The Euler totient of 142 is φ(142) = 70, and the sum of its divisors is σ(142) = 216.

In various numeral systems, 142 is written as 142 in decimal, as 10001110 in binary, and as 0x8E in hexadecimal. In Roman numerals it is CXLII. The common English names are "one hundred forty-two" or, in some varieties, "one hundred and forty-two."

Historically, the year 142 CE falls within the 2nd century and occurred during the reign of the Roman emperor Antoninus Pius (r. 138–161 CE), a period noted for relative stability within the Roman Empire. Beyond calendar reference, 142 does not have a widely recognized mathematical constant or theorem specifically associated with it, but as a semiprime it features in number-theory topics such as factorization and divisor structure.

In everyday use, 142 appears as an ordinary label in addresses, routes, page numbers, and other enumerations. Like many integers, it can also be encountered in combinatorial counts, modular arithmetic exercises, and various algorithmic examples. Overall, 142 is primarily of interest for its basic arithmetic properties and its place in numeral representations.