81584742185 has 4 divisors (see below), whose sum is σ = 97901690628. Its totient is φ = 65267793744.

The previous prime is 81584742163. The next prime is 81584742191. The reversal of 81584742185 is 58124748518.

It is a happy number.

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 11315215129 + 70269527056 = 106373^2 + 265084^2 .

It is a cyclic number.

It is not a de Polignac number, because 81584742185 - 2³² = 77289774889 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, 8158474214 + ... + 8158474223.

It is an arithmetic number, because the mean of its divisors is an integer number (24475422657).

Almost surely, 2^81584742185 is an apocalyptic number.

It is an amenable number.

81584742185 is a deficient number, since it is larger than the sum of its proper divisors (16316948443).

81584742185 is a wasteful number, since it uses less digits than its factorization.

81584742185 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16316948442.

The product of its digits is 2867200, while the sum is 53.

The spelling of 81584742185 in words is "eighty-one billion, five hundred eighty-four million, seven hundred forty-two thousand, one hundred eighty-five".