81673271261 has 4 divisors (see below), whose sum is σ = 81728420124. Its totient is φ = 81618122400.

The previous prime is 81673271227. The next prime is 81673271279. The reversal of 81673271261 is 16217237618.

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 56403400036 + 25269871225 = 237494^2 + 158965^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81673271261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81673271221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27572210 + ... + 27575171.

It is an arithmetic number, because the mean of its divisors is an integer number (20432105031).

Almost surely, 2^81673271261 is an apocalyptic number.

It is an amenable number.

81673271261 is a deficient number, since it is larger than the sum of its proper divisors (55148863).

81673271261 is a wasteful number, since it uses less digits than its factorization.

81673271261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55148862.

The product of its digits is 169344, while the sum is 44.

The spelling of 81673271261 in words is "eighty-one billion, six hundred seventy-three million, two hundred seventy-one thousand, two hundred sixty-one".