Abstract. Let m, n, k and c be positive integers. Let ν 2 (k) be the 2-adic valuation of k. By S(n, k) we denote the Stirling numbers of the second kind. In this paper, we first establish a convolution identity of the Stirling numbers of the second kind and provide a detailed 2-adic analysis to the Stirling numbers of the second kind. Consequently, we show that if 2 ≤ m ≤ n and c is odd, then ν 2 (S(c2 n+1 , 2 m − 1) − S(c2 n , 2 m − 1)) = n + 1 except when n = m = 2 and c = 1, in which case ν 2 (S(8, 3) − S(4, 3)) = 6. This solves a conjecture of Lengyel proposed in 2009.