158 = 2 x 79.
158 is the maximum number of regions into which 13 circles divide the plane.
158 is the smallest number such that the sum of the number and its reverse is a nonpalindromic prime: 158 + 851 = 1009, and 1009 is a nonpalindromic prime.
158 is the sum of the first nine Mersenne prime exponents: 2 + 3 + 5 + 7 + 13 + 17 + 19 + 31 + 61 = 158.
Source: Number Gossip