What is Chinese remainder theorem?

The Chinese remainder theorem is a theorem in number theory that describes a way to solve a system of simultaneous congruences. It states that if one knows the remainders of the division of an integer by several pairwise coprime integers, then one can determine uniquely the remainder of the division of the integer by the product of these integers, under certain conditions. The theorem is named after the Chinese mathematician Sun Tzu, although it was first described by the Chinese mathematician Qin Jiushao in the 13th century. The Chinese remainder theorem has applications in cryptography, computer science, and other fields.