91191819181 has 4 divisors (see below), whose sum is σ = 94336364700. Its totient is φ = 88047273664.

The previous prime is 91191819091. The next prime is 91191819193. The reversal of 91191819181 is 18191819119.

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 58779578025 + 32412241156 = 242445^2 + 180034^2 .

It is a cyclic number.

It is not a de Polignac number, because 91191819181 - 2¹¹ = 91191817133 is a prime.

It is a super-2 number, since 2×91191819181² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91191819581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1572272716 + ... + 1572272773.

It is an arithmetic number, because the mean of its divisors is an integer number (23584091175).

Almost surely, 2^91191819181 is an apocalyptic number.

It is an amenable number.

91191819181 is a deficient number, since it is larger than the sum of its proper divisors (3144545519).

91191819181 is a wasteful number, since it uses less digits than its factorization.

91191819181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3144545518.

The product of its digits is 46656, while the sum is 49.

The spelling of 91191819181 in words is "ninety-one billion, one hundred ninety-one million, eight hundred nineteen thousand, one hundred eighty-one".