A 64-bit integer is a data type used in computing that can represent whole numbers using 64 bits, or binary digits. This allows it to store a wide range of values, from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 in signed form. The large range makes it suitable for applications requiring precise calculations, such as scientific computations and large-scale data processing. In programming, 64-bit integers are commonly used in languages like C, C++, and Java. They are essential for tasks that involve large datasets or require high precision, ensuring that calculations remain accurate without overflow errors that can occur with smaller integer types.