81904666 has 16 divisors (see below), whose sum is σ = 128136960. Its totient is φ = 39219840.

The previous prime is 81904661. The next prime is 81904681. The reversal of 81904666 is 66640918.

It is not an unprimeable number, because it can be changed into a prime (81904661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 796 + ... + 12823.

It is an arithmetic number, because the mean of its divisors is an integer number (8008560).

Almost surely, 2^81904666 is an apocalyptic number.

81904666 is a deficient number, since it is larger than the sum of its proper divisors (46232294).

81904666 is a wasteful number, since it uses less digits than its factorization.

81904666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13749.

The product of its (nonzero) digits is 62208, while the sum is 40.

The square root of 81904666 is about 9050.1196677171. The cubic root of 81904666 is about 434.2797187352.

The spelling of 81904666 in words is "eighty-one million, nine hundred four thousand, six hundred sixty-six".