(number theory) Given coprime positive integers a, b and c, such that a + b = c, and d the radical of abc (the product of its distinct prime factors), the conjecture that d is usually not much smaller than c (in other words, that if a and b are divisible by large powers of primes, then c usually is not).

(mathematics) A conjecture stating that, if Aˣ+Bʸ=Cᶻ, where A, B, C, x, y, and z are positive integers with x, y, z > 2, then A, B, and C have a common prime factor.

(mathematics) A conjecture in number theory regarding the sequences generated by applying the forward difference operator to consecutive prime numbers and leaving the results unsigned, and then repeating this process on consecutive terms in the resulting sequence, and so forth. The first term in every such sequence appears to be 1.

(mathematics, physics) An attempt to understand the mirror symmetry conjecture, an issue in theoretical physics and mathematics.

(mathematics) The proven conjecture that a regular hexagonal grid, or honeycomb, is the best way to divide a surface into regions of equal area with the smallest total perimeter.

(mathematics) The conjecture that the process of taking a number n and, if n is even, dividing it by 2, or if n is odd, multiplying it by 3 and adding 1, then repeating this process, will eventually yield 1.

(graph theory) A conjecture concerning the connection between graph coloring and the tensor product of graphs. A counterexample was found in 2019.

(number theory) The conjecture that, for a finite set of linear forms a₁ + b₁n, a₂ + b₂n, ..., aₖ + bₖn with bᵢ ≥ 1, there are infinitely many positive integers n for which they are all prime, unless there is a congruence condition preventing this.

(number theory) The conjecture that, for any positive even number n, there are infinitely many prime gaps of size n.

(number theory) The conjecture that there are at least four prime numbers between (pₙ)² and (pₙ₊₁)², where pₙ is the nth prime number, for every n ≥ 2.