11×13

11×13 denotes the multiplication of the integers 11 and 13. The product is 143. Both factors are prime numbers; the result is a semiprime, being the product of exactly two primes.

11 and 13 are twin primes, a pair of primes separated by 2. Because they are distinct primes, 11×13 is squarefree and has exactly four positive divisors: 1, 11, 13, and 143.

In geometry, a rectangle with sides 11 and 13 has an area of 143 square units. A grid consisting of 11 by 13 unit squares contains 143 individual cells.

In numeral representations, 143 is the decimal representation of the product 11×13. In Roman numerals, 143 is written as CXLIII. In other bases, its representation changes (for example, in base 12, 143 decimal is BB).

Because multiplication is commutative, 11×13 equals 13×11. The expression is often used as a straightforward example in teaching basic multiplication and in illustrating properties of prime factors and semiprimes.