81181605258 has 24 divisors (see below), whose sum is σ = 189423746148. Its totient is φ = 24978955392.

The previous prime is 81181605251. The next prime is 81181605277. The reversal of 81181605258 is 85250618118.

81181605258 is a `hidden beast` number, since 8 + 1 + 18 + 1 + 605 + 25 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 70874685729 + 10306919529 = 266223^2 + 101523^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81181605251) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 173464735 + ... + 173465202.

Almost surely, 2^81181605258 is an apocalyptic number.

81181605258 is an abundant number, since it is smaller than the sum of its proper divisors (108242140890).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81181605258 is a wasteful number, since it uses less digits than its factorization.

81181605258 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 346929958 (or 346929955 counting only the distinct ones).

The product of its (nonzero) digits is 153600, while the sum is 45.

The spelling of 81181605258 in words is "eighty-one billion, one hundred eighty-one million, six hundred five thousand, two hundred fifty-eight".