81573666 has 16 divisors (see below), whose sum is σ = 166941984. Its totient is φ = 26558784.

The previous prime is 81573659. The next prime is 81573691. The reversal of 81573666 is 66637518.

It is a Curzon 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, 157831 + ... + 158346.

It is an arithmetic number, because the mean of its divisors is an integer number (10433874).

Almost surely, 2^81573666 is an apocalyptic number.

81573666 is a gapful number since it is divisible by the number (86) formed by its first and last digit.

81573666 is an abundant number, since it is smaller than the sum of its proper divisors (85368318).

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

81573666 is a wasteful number, since it uses less digits than its factorization.

81573666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316225.

The product of its digits is 181440, while the sum is 42.

The square root of 81573666 is about 9031.8141034900. The cubic root of 81573666 is about 433.6939130251.

The spelling of 81573666 in words is "eighty-one million, five hundred seventy-three thousand, six hundred sixty-six".