81565805 has 8 divisors (see below), whose sum is σ = 101036544. Its totient is φ = 63147600.

The previous prime is 81565801. The next prime is 81565819. The reversal of 81565805 is 50856518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81565805 - 2² = 81565801 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81565801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 262961 + ... + 263270.

It is an arithmetic number, because the mean of its divisors is an integer number (12629568).

Almost surely, 2^81565805 is an apocalyptic number.

It is an amenable number.

81565805 is a deficient number, since it is larger than the sum of its proper divisors (19470739).

81565805 is a wasteful number, since it uses less digits than its factorization.

81565805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 526267.

The product of its (nonzero) digits is 48000, while the sum is 38.

The square root of 81565805 is about 9031.3789091146. The cubic root of 81565805 is about 433.6799813340.

The spelling of 81565805 in words is "eighty-one million, five hundred sixty-five thousand, eight hundred five".