44 is the smallest number that is the sum of a reversible pair of non-palindromic primes: 13 + 31 = 44.
44 is the first number such that it and the next number are the product of a prime and another distinct prime squared: 44 = 22 x 11 and 45 = 32 x 5.
44 is the maximum number of regions into which the plane can be divided by seven circles.
44 is the atomic number of the chemical element ruthenium.
Source: Number Gossip
