81993739905 has 192 divisors, whose sum is σ = 187008307200. Its totient is φ = 32196994560.

The previous prime is 81993739871. The next prime is 81993739909. The reversal of 81993739905 is 50993739918.

It is not a de Polignac number, because 81993739905 - 2¹⁶ = 81993674369 is a prime.

It is a hoax number, since the sum of its digits (63) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (81993739909) by changing a digit.

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 191 ways as a sum of consecutive naturals, for example, 28900147 + ... + 28902983.

It is an arithmetic number, because the mean of its divisors is an integer number (974001600).

Almost surely, 2^81993739905 is an apocalyptic number.

It is an amenable number.

81993739905 is an abundant number, since it is smaller than the sum of its proper divisors (105014567295).

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

81993739905 is a wasteful number, since it uses less digits than its factorization.

81993739905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3324 (or 3321 counting only the distinct ones).

The product of its (nonzero) digits is 16533720, while the sum is 63.

The spelling of 81993739905 in words is "eighty-one billion, nine hundred ninety-three million, seven hundred thirty-nine thousand, nine hundred five".