How many flip-flops are required to divide a signal frequency by 16?

Each flip-flop in a digital counter circuit divides the input frequency by 2. When multiple flip-flops are cascaded (connected in a series), their frequency division factors multiply together. The total division factor is equal to 2 raised to the power of the number of flip-flops (2^n). Therefore, a single flip-flop divides by 2, two divide by 4, three divide by 8, and four divide by 16 (2 x 2 x 2 x 2 = 16). Connecting 8 or 16 flip-flops would divide the frequency by 256 or 65,536 respectively, which is far more division than this question requires.