81395665 has 16 divisors (see below), whose sum is σ = 105412608. Its totient is φ = 59979456.

The previous prime is 81395653. The next prime is 81395683. The reversal of 81395665 is 56659318.

It is a cyclic number.

It is not a de Polignac number, because 81395665 - 2¹³ = 81387473 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38424 + ... + 40486.

It is an arithmetic number, because the mean of its divisors is an integer number (6588288).

Almost surely, 2^81395665 is an apocalyptic number.

It is an amenable number.

81395665 is a deficient number, since it is larger than the sum of its proper divisors (24016943).

81395665 is a wasteful number, since it uses less digits than its factorization.

81395665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2688.

The product of its digits is 194400, while the sum is 43.

The square root of 81395665 is about 9021.9546108368. The cubic root of 81395665 is about 433.3782303909.

The spelling of 81395665 in words is "eighty-one million, three hundred ninety-five thousand, six hundred sixty-five".