81765805 has 32 divisors (see below), whose sum is σ = 112907520. Its totient is φ = 56263680.

The previous prime is 81765791. The next prime is 81765811. The reversal of 81765805 is 50856718.

It is not a de Polignac number, because 81765805 - 2⁵ = 81765773 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 137589 + ... + 138181.

It is an arithmetic number, because the mean of its divisors is an integer number (3528360).

Almost surely, 2^81765805 is an apocalyptic number.

It is an amenable number.

81765805 is a deficient number, since it is larger than the sum of its proper divisors (31141715).

81765805 is a wasteful number, since it uses less digits than its factorization.

81765805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 741.

The product of its (nonzero) digits is 67200, while the sum is 40.

The square root of 81765805 is about 9042.4446362696. Note that the first 3 decimals coincide. The cubic root of 81765805 is about 434.0341542631.

The spelling of 81765805 in words is "eighty-one million, seven hundred sixty-five thousand, eight hundred five".