8

This number is a composite.

Just showing those entries submitted by 'Gaydos': (Click here to show all)

8 is the smallest cube that is the sum of two consecutive Sophie Germain primes (3 + 5). Can you find the next cube with this property? [Gaydos]

8 is the last digit to appear in both a prime number and its prime index, first appearing in 787 and 138. The other 9 digits all first appear in smaller prime-prime index pairs. [Gaydos]