642

642 is a natural number that follows 641 and precedes 643. It is an even composite integer.

In mathematics, 642 factors into 2 × 3 × 107, so its divisors are 1, 2, 3, 6, 107, 214, 321, and 642. It is not a prime, square, or cube. The sum of its digits is 12, giving a digital root of 3, and it is divisible by 3 and 6.

In different numeral systems, 642 is written as 1010000010 in binary, 0o1202 in octal, and 0x282 in hexadecimal. In Roman numerals, it is DCXLII.

Historically, the year 642 CE falls in the early medieval period. It is associated with the era of rapid expansion of the Islamic Caliphate, and in that year the conquest of Egypt is often dated to its conclusion, with the city of Fustat established as the new capital of Islamic Egypt.

As a fixed integer, 642 appears in various mathematical and applied contexts, including arithmetic, number theory, and computer science when discussing numeric representations and divisors. It does not have a widely recognized cultural or scientific designation beyond its role as a specific integer, but like other natural numbers, it participates in patterns and sequences that mathematicians study.