34 = 2 x 17.
34 is the ninth Fibonacci number.
34 is the smallest number with the property that it and its neighbors have the same number of divisors (four): 33 = 3 x 11; 34 = 2 x 17; 35 = 5 x 7.
The rows and columns of a 4 x 4 magic square always total 34.
34 has a representation as a sum of two squares: 34 = 32 + 52.
34 is the smallest number with four representations as a sum of two primes: 34 = 3 + 31 = 5 + 29 = 11 + 23 = 17 + 17.
34 is 22 in base 16.
Source: Number Gossip