990121221 has 12 divisors (see below), whose sum is σ = 1468828972. Its totient is φ = 642240576.

The previous prime is 990121211. The next prime is 990121247. The reversal of 990121221 is 122121099.

It can be written as a sum of positive squares in 2 ways, for example, as 436224996 + 553896225 = 20886^2 + 23535^2 .

It is not a de Polignac number, because 990121221 - 2⁵ = 990121189 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 (990121201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1486336 + ... + 1487001.

Almost surely, 2^990121221 is an apocalyptic number.

It is an amenable number.

990121221 is a deficient number, since it is larger than the sum of its proper divisors (478707751).

990121221 is a wasteful number, since it uses less digits than its factorization.

990121221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2973380 (or 2973377 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 990121221 is about 31466.1917142828. The cubic root of 990121221 is about 996.6961703974.

The spelling of 990121221 in words is "nine hundred ninety million, one hundred twenty-one thousand, two hundred twenty-one".