999998821 has 4 divisors (see below), whose sum is σ = 1000184332. Its totient is φ = 999813312.

The previous prime is 999998801. The next prime is 999998843. The reversal of 999998821 is 128899999.

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 961868196 + 38130625 = 31014^2 + 6175^2 .

It is a cyclic number.

It is not a de Polignac number, because 999998821 - 2⁵ = 999998789 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999998801) 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, 84420 + ... + 95533.

It is an arithmetic number, because the mean of its divisors is an integer number (250046083).

Almost surely, 2^999998821 is an apocalyptic number.

It is an amenable number.

999998821 is a deficient number, since it is larger than the sum of its proper divisors (185511).

999998821 is a wasteful number, since it uses less digits than its factorization.

999998821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185510.

The product of its digits is 7558272, while the sum is 64.

The square root of 999998821 is about 31622.7579600515. The cubic root of 999998821 is about 999.9996069998. Note that the first 3 decimals are identical.

The spelling of 999998821 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, eight hundred twenty-one".