91209436081 has 3 divisors (see below), whose sum is σ = 91209738091. Its totient is φ = 91209134072.

The previous prime is 91209436069. The next prime is 91209436091. The reversal of 91209436081 is 18063490219.

It is a happy number.

The square root of 91209436081 is 302009.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 18063490219 = 4789 ⋅3771871.

It can be written as a sum of positive squares in only one way, i.e., 174477681 + 91034958400 = 13209^2 + 301720^2 .

It is not a de Polignac number, because 91209436081 - 2⁵ = 91209436049 is a prime.

It is a super-2 number, since 2×91209436081² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91209436051) 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 2 ways as a sum of consecutive naturals, for example, 151005 + ... + 453013.

Almost surely, 2^91209436081 is an apocalyptic number.

91209436081 is the 302009-th square number.

91209436081 is the 151005-th centered octagonal number.

It is an amenable number.

91209436081 is a deficient number, since it is larger than the sum of its proper divisors (302010).

91209436081 is an frugal number, since it uses more digits than its factorization.

91209436081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 604018 (or 302009 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 43.

The spelling of 91209436081 in words is "ninety-one billion, two hundred nine million, four hundred thirty-six thousand, eighty-one".