81668804139 has 24 divisors (see below), whose sum is σ = 127100365392. Its totient is φ = 50233988160.

The previous prime is 81668804131. The next prime is 81668804141. The reversal of 81668804139 is 93140886618.

It is not a de Polignac number, because 81668804139 - 2³ = 81668804131 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81668804131) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 85549 + ... + 413105.

It is an arithmetic number, because the mean of its divisors is an integer number (5295848558).

Almost surely, 2^81668804139 is an apocalyptic number.

81668804139 is a deficient number, since it is larger than the sum of its proper divisors (45431561253).

81668804139 is a wasteful number, since it uses less digits than its factorization.

81668804139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329707 (or 329704 counting only the distinct ones).

The product of its (nonzero) digits is 1990656, while the sum is 54.

The spelling of 81668804139 in words is "eighty-one billion, six hundred sixty-eight million, eight hundred four thousand, one hundred thirty-nine".