81861690568 has 32 divisors (see below), whose sum is σ = 175449585600. Its totient is φ = 35077246272.

The previous prime is 81861690553. The next prime is 81861690569. The reversal of 81861690568 is 86509616818.

It is not an unprimeable number, because it can be changed into a prime (81861690569) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 187746 + ... + 446062.

It is an arithmetic number, because the mean of its divisors is an integer number (5482799550).

Almost surely, 2^81861690568 is an apocalyptic number.

It is an amenable number.

81861690568 is an abundant number, since it is smaller than the sum of its proper divisors (93587895032).

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

81861690568 is a wasteful number, since it uses less digits than its factorization.

81861690568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263989 (or 263985 counting only the distinct ones).

The product of its (nonzero) digits is 4976640, while the sum is 58.

The spelling of 81861690568 in words is "eighty-one billion, eight hundred sixty-one million, six hundred ninety thousand, five hundred sixty-eight".