81431904 has 96 divisors (see below), whose sum is σ = 232043616. Its totient is φ = 24903680.

The previous prime is 81431879. The next prime is 81431923. The reversal of 81431904 is 40913418.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 66304 + ... + 67520.

It is an arithmetic number, because the mean of its divisors is an integer number (2417121).

Almost surely, 2^81431904 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 81431904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116021808).

81431904 is an abundant number, since it is smaller than the sum of its proper divisors (150611712).

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

81431904 is a wasteful number, since it uses less digits than its factorization.

81431904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1288 (or 1280 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 81431904 is about 9023.9627658806. The cubic root of 81431904 is about 433.4425371059.

It can be divided in two parts, 81 and 431904, that added together give a triangular number (431985 = T₉₂₉).

The spelling of 81431904 in words is "eighty-one million, four hundred thirty-one thousand, nine hundred four".