81787120128 has 240 divisors, whose sum is σ = 276347687616. Its totient is φ = 22797434880.

The previous prime is 81787120117. The next prime is 81787120189. The reversal of 81787120128 is 82102178718.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1291575 + ... + 1353417.

Almost surely, 2^81787120128 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 81787120128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138173843808).

81787120128 is an abundant number, since it is smaller than the sum of its proper divisors (194560567488).

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

81787120128 is a wasteful number, since it uses less digits than its factorization.

81787120128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61915 (or 61896 counting only the distinct ones).

The product of its (nonzero) digits is 100352, while the sum is 45.

The spelling of 81787120128 in words is "eighty-one billion, seven hundred eighty-seven million, one hundred twenty thousand, one hundred twenty-eight".