81971457868 has 12 divisors (see below), whose sum is σ = 143453787232. Its totient is φ = 40984661520.

The previous prime is 81971457863. The next prime is 81971457877. The reversal of 81971457868 is 86875417918.

It is not an unprimeable number, because it can be changed into a prime (81971457863) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 79443 + ... + 412618.

Almost surely, 2^81971457868 is an apocalyptic number.

It is an amenable number.

81971457868 is a deficient number, since it is larger than the sum of its proper divisors (61482329364).

81971457868 is a wasteful number, since it uses less digits than its factorization.

81971457868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 533712 (or 533710 counting only the distinct ones).

The product of its digits is 27095040, while the sum is 64.

The spelling of 81971457868 in words is "eighty-one billion, nine hundred seventy-one million, four hundred fifty-seven thousand, eight hundred sixty-eight".