Comprehensive Reference: Number Theory, Prime Decomposition, and Discrete Sequences
Number theory—often hailed by Carl Friedrich Gauss as the Queen of Mathematics—deals with the deep structure of integers ($integers$). From public-key cryptographic security (such as RSA and Elliptic Curve Cryptography) to algorithmic efficiency in computer hardware, discrete arithmetic underpins modern computational civilization.
1. The Fundamental Theorem of Arithmetic
The Fundamental Theorem of Arithmetic asserts that every integer greater than 1 is either a prime number itself or can be represented uniquely as a product of prime numbers, up to the order of the factors:
Where $p_1 < p_2 < \dots < p_k$ are distinct primes, and $a_i \ge 1$ are positive integer exponents. For instance, the canonical prime decomposition of $360$ is $2^3 \times 3^2 \times 5^1$.
Calculating the Total Number of Divisors $\tau(n)$
Using the canonical prime representation, the total count of positive integer divisors $\tau(n)$ is determined without manual trial division by incrementing each prime power by 1 and multiplying the exponents:
For $360 = 2^3 \times 3^2 \times 5^1$, the divisor count is $(3 + 1)(2 + 1)(1 + 1) = 4 \times 3 \times 2 = 24$ total divisors.
2. Euclidean Division, Remainder, and Clock Modulo
Given any integer dividend $A$ and a non-zero divisor $B$, the Euclidean Division Lemma guarantees the existence of unique integers $q$ (quotient) and $r$ (remainder) such that:
In many programming languages, the % operator implements truncated division, meaning that the remainder shares the sign of the dividend. For example:
-13 % 5 = -3 (in JS / C++)
In pure mathematics, modular arithmetic wraps around like the numbers on a clock face, and residue classes are strictly non-negative:
-13 ≡ 2 (mod 5) since -13 = 5 × (-3) + 2
3. Closed-Form Series and Progression Theorems
Evaluating finite summations manually becomes intractable for large indices $n$. Closed-form formulas resolve finite series instantly:
| Series Type | Mathematical Notation | Closed-Form Analytical Formula |
|---|---|---|
| Sum of First n Natural Numbers | 1 + 2 + 3 + ... + n | S = n(n + 1) / 2 |
| Sum of First n Squares | 1² + 2² + ... + n² | S = n(n + 1)(2n + 1) / 6 |
| Sum of First n Cubes | 1³ + 2³ + ... + n³ | S = [n(n + 1) / 2]² |
| Arithmetic Progression (AP) | ∑ [a + (i-1)d] | S = n/2 × [2a + (n - 1)d] |