81904081 has 16 divisors (see below), whose sum is σ = 98178048. Its totient is φ = 66805200.

The previous prime is 81904073. The next prime is 81904087. The reversal of 81904081 is 18040918.

It is not a de Polignac number, because 81904081 - 2³ = 81904073 is a prime.

It is a super-2 number, since 2×81904081² = 13416556968909122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81904087) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32766 + ... + 35176.

It is an arithmetic number, because the mean of its divisors is an integer number (6136128).

Almost surely, 2^81904081 is an apocalyptic number.

It is an amenable number.

81904081 is a deficient number, since it is larger than the sum of its proper divisors (16273967).

81904081 is a wasteful number, since it uses less digits than its factorization.

81904081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2652.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 81904081 is about 9050.0873476448. The cubic root of 81904081 is about 434.2786847924.

Adding to 81904081 its reverse (18040918), we get a palindrome (99944999).

The spelling of 81904081 in words is "eighty-one million, nine hundred four thousand, eighty-one".