43

43 is the natural number that follows 42 and precedes 44. In mathematics, 43 is a prime number, the 14th prime, and is part of the twin prime pair with 41. It is odd and has representations in multiple bases: 101011 in binary, 53 in octal, and 2B in hexadecimal; in Roman numerals it is XLIII.

In science, 43 is the atomic number of technetium (Tc). Technetium was the first element to be artificially produced and has no stable isotopes. It was named from the Greek technetos, meaning artificial. The isotope technetium-99m is widely used in diagnostic imaging.

In computing and notation, the decimal ASCII code 43 corresponds to the plus sign (+). The international telephone country code for Austria is +43. Messier 43, also known as De Mairan's Nebula, is a small emission nebula in the constellation Orion, located near Messier 42.

Calendar and culture notes: day 43 of the year falls on February 12 in both common and leap years. The number 43 also appears in various cultural references as a numerical marker rather than a symbolic meaning, reflecting its role as a ordinary, indivisible prime in number theory.