81136904 has 8 divisors (see below), whose sum is σ = 152131710. Its totient is φ = 40568448.

The previous prime is 81136879. The next prime is 81136927. The reversal of 81136904 is 40963118.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 51868804 + 29268100 = 7202^2 + 5410^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5071049 + ... + 5071064.

Almost surely, 2^81136904 is an apocalyptic number.

It is an amenable number.

81136904 is a deficient number, since it is larger than the sum of its proper divisors (70994806).

81136904 is a wasteful number, since it uses less digits than its factorization.

81136904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10142119 (or 10142115 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 81136904 is about 9007.6025667211. The cubic root of 81136904 is about 432.9184989911.

The spelling of 81136904 in words is "eighty-one million, one hundred thirty-six thousand, nine hundred four".