81501904 has 40 divisors (see below), whose sum is σ = 172935360. Its totient is φ = 36902400.

The previous prime is 81501881. The next prime is 81501913. The reversal of 81501904 is 40910518.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53992 + ... + 55480.

It is an arithmetic number, because the mean of its divisors is an integer number (4323384).

Almost surely, 2^81501904 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 81501904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86467680).

81501904 is an abundant number, since it is smaller than the sum of its proper divisors (91433456).

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

81501904 is a wasteful number, since it uses less digits than its factorization.

81501904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1819 (or 1813 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 81501904 is about 9027.8404948249. The cubic root of 81501904 is about 433.5666992848.

The spelling of 81501904 in words is "eighty-one million, five hundred one thousand, nine hundred four".