81906765 has 16 divisors (see below), whose sum is σ = 138760128. Its totient is φ = 41113856.

The previous prime is 81906719. The next prime is 81906823. The reversal of 81906765 is 56760918.

It is a cyclic number.

It is not a de Polignac number, because 81906765 - 2⁷ = 81906637 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 (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 160347 + ... + 160856.

It is an arithmetic number, because the mean of its divisors is an integer number (8672508).

Almost surely, 2^81906765 is an apocalyptic number.

81906765 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81906765 is a deficient number, since it is larger than the sum of its proper divisors (56853363).

81906765 is a wasteful number, since it uses less digits than its factorization.

81906765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321228.

The product of its (nonzero) digits is 90720, while the sum is 42.

The square root of 81906765 is about 9050.2356322916. The cubic root of 81906765 is about 434.2834285171.

The spelling of 81906765 in words is "eighty-one million, nine hundred six thousand, seven hundred sixty-five".