81636942564 has 72 divisors (see below), whose sum is σ = 223580316960. Its totient is φ = 25015963392.

The previous prime is 81636942559. The next prime is 81636942599. The reversal of 81636942564 is 46524963618.

81636942564 is a `hidden beast` number, since 8 + 1 + 6 + 36 + 9 + 42 + 564 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 81636942564.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1524774 + ... + 1577405.

It is an arithmetic number, because the mean of its divisors is an integer number (3105282180).

Almost surely, 2^81636942564 is an apocalyptic number.

It is an amenable number.

81636942564 is an abundant number, since it is smaller than the sum of its proper divisors (141943374396).

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

81636942564 is a wasteful number, since it uses less digits than its factorization.

81636942564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3102249 (or 3102244 counting only the distinct ones).

The product of its digits is 7464960, while the sum is 54.

The spelling of 81636942564 in words is "eighty-one billion, six hundred thirty-six million, nine hundred forty-two thousand, five hundred sixty-four".