4²¹⁴.
Note that if the exponent is ODD , the unit digit is always 4:
4¹ = 4, 4³ = 64, 4⁵ = 1024 ... 4¹⁵ = 1,073,741,824, etc.
But when the exponent is EVEN, the last digit is always 6:
4² = 16, 4⁶ = 4,096, 4⁸ = 65,536, ...4¹⁶ = 4,294,967,296
By induction we can say that the last digit of 4²¹⁴ is 6, because the exponent is EVEN
