81556445251 has 4 divisors (see below), whose sum is σ = 81560404552. Its totient is φ = 81552485952.

The previous prime is 81556445239. The next prime is 81556445261. The reversal of 81556445251 is 15254465518.

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

It is a cyclic number.

It is not a de Polignac number, because 81556445251 - 2¹¹ = 81556443203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81556445261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1948590 + ... + 1990003.

It is an arithmetic number, because the mean of its divisors is an integer number (20390101138).

Almost surely, 2^81556445251 is an apocalyptic number.

81556445251 is a deficient number, since it is larger than the sum of its proper divisors (3959301).

81556445251 is a wasteful number, since it uses less digits than its factorization.

81556445251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3959300.

The product of its digits is 960000, while the sum is 46.

The spelling of 81556445251 in words is "eighty-one billion, five hundred fifty-six million, four hundred forty-five thousand, two hundred fifty-one".