(number theory) An odd natural number k such that k⨯2ⁿ+1 is composite for all natural numbers n.

(UK politics, colloquial) Synonym of 11 Downing Street

(UK politics, colloquial) Synonym of 11 Downing Street

plural of hyperperfect number

(mathematics, number theory) Any natural number n for which, for some positive integer k, n = 1 + k(σ(n) - n - 1), where σ(n) is the sum of the positive divisors of n.

A squarefree integer with at least three prime factors which fall into the pattern p_x=ap_x-1+b, where a and b are some integer constants and x is the index number of each prime factor in the factorization, sorted from lowest to highest.

A number of the form xʸ+yˣ, where x and y are integers greater than 1.

plural of Zeisel number

plural of Leyland number

plural of Laws number