71 (number)

71 is the natural number following 70 and preceding 72.

In mathematics

71 is the 20th prime number. Because both rearrangements of its digits are prime numbers, 71 is an emirp and more generally a permutable prime.
71 is a centered heptagonal number.
It is a regular prime, a Ramanujan prime, a Higgs prime, and a good prime.
It is a Pillai prime, since is divisible by 71, but 71 is not one more than a multiple of 9.
It is part of the last known pair of Brown numbers, since.
71 is the smallest of thirty-one discriminants of imaginary quadratic fields with class number of 7, negated.
71 is the largest number which occurs as a prime factor of an order of a sporadic simple group, the largest Supersingular [prime (moonshine theory)|supersingular prime].