81806512 has 20 divisors (see below), whose sum is σ = 159302800. Its totient is φ = 40696128.

The previous prime is 81806467. The next prime is 81806537. The reversal of 81806512 is 21560818.

It is a super-2 number, since 2×81806512² = 13384610811212288, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9663 + ... + 16030.

It is an arithmetic number, because the mean of its divisors is an integer number (7965140).

Almost surely, 2^81806512 is an apocalyptic number.

It is an amenable number.

81806512 is a deficient number, since it is larger than the sum of its proper divisors (77496288).

81806512 is a wasteful number, since it uses less digits than its factorization.

81806512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25900 (or 25894 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 81806512 is about 9044.6952408580. The cubic root of 81806512 is about 434.1061700938.

The spelling of 81806512 in words is "eighty-one million, eight hundred six thousand, five hundred twelve".