What is the unit digit of 2 the power of 40?

To find the unit digit of 2 raised to the power of 40, we can observe a pattern. The unit digit of powers of 2 cycles in a pattern: 2, 4, 8, 6. Since 40 is a multiple of 4, the unit digit of 2^40 will be the fourth number in the pattern, which is 6. Thus, the unit digit of 2^40 is 6.