71991321856 has 36 divisors (see below), whose sum is σ = 149949328032. Its totient is φ = 34430629376.

The previous prime is 71991321781. The next prime is 71991321893. The reversal of 71991321856 is 65812319917.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6107506 + ... + 6119281.

It is an arithmetic number, because the mean of its divisors is an integer number (4165259112).

Almost surely, 2^71991321856 is an apocalyptic number.

It is an amenable number.

71991321856 is an abundant number, since it is smaller than the sum of its proper divisors (77958006176).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

71991321856 is a wasteful number, since it uses less digits than its factorization.

71991321856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12226826 (or 12226812 counting only the distinct ones).

The product of its digits is 816480, while the sum is 52.

The spelling of 71991321856 in words is "seventy-one billion, nine hundred ninety-one million, three hundred twenty-one thousand, eight hundred fifty-six".