9900990221 has 4 divisors (see below), whose sum is σ = 9912598332. Its totient is φ = 9889382112.

The previous prime is 9900990217. The next prime is 9900990223. The reversal of 9900990221 is 1220990099.

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 201498025 + 9699492196 = 14195^2 + 98486^2 .

It is a cyclic number.

It is not a de Polignac number, because 9900990221 - 2² = 9900990217 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 (9900990223) 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, 5802776 + ... + 5804481.

It is an arithmetic number, because the mean of its divisors is an integer number (2478149583).

Almost surely, 2^9900990221 is an apocalyptic number.

It is an amenable number.

9900990221 is a deficient number, since it is larger than the sum of its proper divisors (11608111).

9900990221 is a wasteful number, since it uses less digits than its factorization.

9900990221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11608110.

The product of its (nonzero) digits is 26244, while the sum is 41.

The square root of 9900990221 is about 99503.7196339916. The cubic root of 9900990221 is about 2147.3007569155.

The spelling of 9900990221 in words is "nine billion, nine hundred million, nine hundred ninety thousand, two hundred twenty-one".