81355532544 has 576 divisors, whose sum is σ = 288160830720. Its totient is φ = 22313041920.

The previous prime is 81355532497. The next prime is 81355532579. The reversal of 81355532544 is 44523555318.

It is a happy number.

81355532544 is a `hidden beast` number, since 8 + 1 + 3 + 55 + 53 + 2 + 544 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

It is a super-2 number, since 2×81355532544² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81355532544.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 52385272 + ... + 52386824.

It is an arithmetic number, because the mean of its divisors is an integer number (500279220).

Almost surely, 2^81355532544 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81355532544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144080415360).

81355532544 is an abundant number, since it is smaller than the sum of its proper divisors (206805298176).

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

81355532544 is a wasteful number, since it uses less digits than its factorization.

81355532544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1655 (or 1635 counting only the distinct ones).

The product of its digits is 1440000, while the sum is 45.

The spelling of 81355532544 in words is "eighty-one billion, three hundred fifty-five million, five hundred thirty-two thousand, five hundred forty-four".