81621666684 has 48 divisors (see below), whose sum is σ = 211661604000. Its totient is φ = 27200809728.

The previous prime is 81621666631. The next prime is 81621666701. The reversal of 81621666684 is 48666612618.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 81621666684.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 382804 + ... + 556580.

It is an arithmetic number, because the mean of its divisors is an integer number (4409616750).

Almost surely, 2^81621666684 is an apocalyptic number.

It is an amenable number.

81621666684 is an abundant number, since it is smaller than the sum of its proper divisors (130039937316).

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

81621666684 is a wasteful number, since it uses less digits than its factorization.

81621666684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178139 (or 178131 counting only the distinct ones).

The product of its digits is 3981312, while the sum is 54.

The spelling of 81621666684 in words is "eighty-one billion, six hundred twenty-one million, six hundred sixty-six thousand, six hundred eighty-four".