Integer arithmetic modulo n
Congruence identifies integers differing by a multiple of n.
Key knowledge
For n ≥ 2, a ≡ b (mod n) means n divides a−b. Addition and multiplication descend to the n congruence classes; cancellation or division is not valid without invertibility.
Values and equations
a ≡ b (mod n) ⇔ n | (a−b)
- a, b
- Integer representatives
- n
- Integer modulus at least two
Conditions and scope
- Operands are integers and the same modulus is used.
- A multiplicative inverse exists only for a residue coprime to n.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Section 2.1.1: quotient classes, modular addition/multiplication and noninvertible examples. Simultaneous congruences and Chinese Remainder Theorem, physical pages 1–3.
2026-10-10 · Congruence classes and permitted modular operations.
Entry details
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