81561715384 has 32 divisors (see below), whose sum is σ = 153653947200. Its totient is φ = 40587465600.

The previous prime is 81561715381. The next prime is 81561715393. The reversal of 81561715384 is 48351716518.

It is a happy number.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561715381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6040689 + ... + 6054175.

It is an arithmetic number, because the mean of its divisors is an integer number (4801685850).

Almost surely, 2^81561715384 is an apocalyptic number.

It is an amenable number.

81561715384 is a deficient number, since it is larger than the sum of its proper divisors (72092231816).

81561715384 is a wasteful number, since it uses less digits than its factorization.

81561715384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17023 (or 17019 counting only the distinct ones).

The product of its digits is 806400, while the sum is 49.

The spelling of 81561715384 in words is "eighty-one billion, five hundred sixty-one million, seven hundred fifteen thousand, three hundred eighty-four".