16 (number) 0 to 15 in each column. Sixteen is an even number and a square number. Sixteen is the fourth power of two. Sixteen is the only integer that equals "m" and "n", for some unequal integers "m" and "n" ("m" = 4, "n" = 2, or vice versa). It has this property because 2 = 2 × 2. It is also equal to 2 (see tetration). 16 is the base of the hexadecimal number system, which is used extensively in computer science. In Spanish and Portuguese, 16 is the first compound number (Spanish: "dieciséis", European Portuguese: "dezasseis", Brazilian Portuguese: "dezesseis");
Factorial number system Factorial number system In combinatorics, the factorial number system, also called factoradic, is a mixed radix numeral system adapted to numbering permutations. It is also called factorial base, although factorials do not function as base, but as place value of digits. By converting a number less than "n"! to factorial representation, one obtains a sequence of "n" digits that can be converted to a permutation of "n" in a straightforward way, either using them as Lehmer code or as inversion table representation; in the former case the resulting map from integers to permutations of "n" lists them in lexicographical order.