999998811221 has 2 divisors, whose sum is σ = 999998811222. Its totient is φ = 999998811220.

The previous prime is 999998811199. The next prime is 999998811223. The reversal of 999998811221 is 122118899999.

999998811221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 864228670321 + 135770140900 = 929639^2 + 368470^2 .

It is a cyclic number.

It is not a de Polignac number, because 999998811221 - 2³⁰ = 998925069397 is a prime.

Together with 999998811223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999998811223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499999405610 + 499999405611.

It is an arithmetic number, because the mean of its divisors is an integer number (499999405611).

Almost surely, 2^999998811221 is an apocalyptic number.

It is an amenable number.

999998811221 is a deficient number, since it is larger than the sum of its proper divisors (1).

999998811221 is an equidigital number, since it uses as much as digits as its factorization.

999998811221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15116544, while the sum is 68.

The spelling of 999998811221 in words is "nine hundred ninety-nine billion, nine hundred ninety-eight million, eight hundred eleven thousand, two hundred twenty-one".