90999999221 has 4 divisors (see below), whose sum is σ = 91153456812. Its totient is φ = 90846541632.

The previous prime is 90999999197. The next prime is 90999999241. The reversal of 90999999221 is 12299999909.

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 54856666225 + 36143332996 = 234215^2 + 190114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-90999999221 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 (90999999241) 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, 76727906 + ... + 76729091.

It is an arithmetic number, because the mean of its divisors is an integer number (22788364203).

Almost surely, 2^90999999221 is an apocalyptic number.

It is an amenable number.

90999999221 is a deficient number, since it is larger than the sum of its proper divisors (153457591).

90999999221 is a wasteful number, since it uses less digits than its factorization.

90999999221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153457590.

The product of its (nonzero) digits is 19131876, while the sum is 68.

The spelling of 90999999221 in words is "ninety billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, two hundred twenty-one".