81558729900 has 180 divisors, whose sum is σ = 267568702632. Its totient is φ = 21486781440.

The previous prime is 81558729881. The next prime is 81558729919. The reversal of 81558729900 is 992785518.

81558729900 is a `hidden beast` number, since 81 + 558 + 7 + 2 + 9 + 9 + 0 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81558729881) and next prime (81558729919).

It is a tau number, because it is divible by the number of its divisors (180).

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

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 611644 + ... + 732956.

Almost surely, 2^81558729900 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 81558729900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (133784351316).

81558729900 is an abundant number, since it is smaller than the sum of its proper divisors (186009972732).

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

81558729900 is a wasteful number, since it uses less digits than its factorization.

81558729900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121422 (or 121406 counting only the distinct ones).

The product of its (nonzero) digits is 1814400, while the sum is 54.

The spelling of 81558729900 in words is "eighty-one billion, five hundred fifty-eight million, seven hundred twenty-nine thousand, nine hundred".