81999024978 has 128 divisors (see below), whose sum is σ = 184638504960. Its totient is φ = 24106844160.

The previous prime is 81999024949. The next prime is 81999025001. The reversal of 81999024978 is 87942099918.

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, 78920583 + ... + 78921621.

It is an arithmetic number, because the mean of its divisors is an integer number (1442488320).

Almost surely, 2^81999024978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81999024978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92319252480).

81999024978 is an abundant number, since it is smaller than the sum of its proper divisors (102639479982).

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

81999024978 is a wasteful number, since it uses less digits than its factorization.

81999024978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1472.

The product of its (nonzero) digits is 23514624, while the sum is 66.

The spelling of 81999024978 in words is "eighty-one billion, nine hundred ninety-nine million, twenty-four thousand, nine hundred seventy-eight".