81597785 has 4 divisors (see below), whose sum is σ = 97917348. Its totient is φ = 65278224.

The previous prime is 81597743. The next prime is 81597811. The reversal of 81597785 is 58779518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 37295449 + 44302336 = 6107^2 + 6656^2 .

It is a cyclic number.

It is not a de Polignac number, because 81597785 - 2²² = 77403481 is a prime.

It is a Duffinian number.

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, 8159774 + ... + 8159783.

It is an arithmetic number, because the mean of its divisors is an integer number (24479337).

Almost surely, 2^81597785 is an apocalyptic number.

It is an amenable number.

81597785 is a deficient number, since it is larger than the sum of its proper divisors (16319563).

81597785 is a wasteful number, since it uses less digits than its factorization.

81597785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16319562.

The product of its digits is 705600, while the sum is 50.

The square root of 81597785 is about 9033.1492293662. The cubic root of 81597785 is about 433.7366524419.

The spelling of 81597785 in words is "eighty-one million, five hundred ninety-seven thousand, seven hundred eighty-five".