81540353664 has 768 divisors, whose sum is σ = 323352207360. Its totient is φ = 19058688000.

The previous prime is 81540353639. The next prime is 81540353669. The reversal of 81540353664 is 46635304518.

81540353664 is a `hidden beast` number, since 8 + 1 + 54 + 0 + 3 + 536 + 64 = 666.

It is not an unprimeable number, because it can be changed into a prime (81540353669) 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 95 ways as a sum of consecutive naturals, for example, 34682089 + ... + 34684439.

It is an arithmetic number, because the mean of its divisors is an integer number (421031520).

Almost surely, 2^81540353664 is an apocalyptic number.

81540353664 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81540353664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (161676103680).

81540353664 is an abundant number, since it is smaller than the sum of its proper divisors (241811853696).

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

81540353664 is a wasteful number, since it uses less digits than its factorization.

81540353664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2429 (or 2414 counting only the distinct ones).

The product of its (nonzero) digits is 1036800, while the sum is 45.

The spelling of 81540353664 in words is "eighty-one billion, five hundred forty million, three hundred fifty-three thousand, six hundred sixty-four".