90918191909 has 4 divisors (see below), whose sum is σ = 90944404140. Its totient is φ = 90891979680.

The previous prime is 90918191887. The next prime is 90918191933. The reversal of 90918191909 is 90919181909.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90919181909 = 307 ⋅296153687.

It can be written as a sum of positive squares in 2 ways, for example, as 6687641284 + 84230550625 = 81778^2 + 290225^2 .

It is a cyclic number.

It is not a de Polignac number, because 90918191909 - 2¹⁶ = 90918126373 is a prime.

It is a super-2 number, since 2×90918191909² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90918191939) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13100912 + ... + 13107849.

It is an arithmetic number, because the mean of its divisors is an integer number (22736101035).

Almost surely, 2^90918191909 is an apocalyptic number.

It is an amenable number.

90918191909 is a deficient number, since it is larger than the sum of its proper divisors (26212231).

90918191909 is a wasteful number, since it uses less digits than its factorization.

90918191909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26212230.

The product of its (nonzero) digits is 472392, while the sum is 56.

The spelling of 90918191909 in words is "ninety billion, nine hundred eighteen million, one hundred ninety-one thousand, nine hundred nine".