999998921 has 2 divisors, whose sum is σ = 999998922. Its totient is φ = 999998920.

The previous prime is 999998917. The next prime is 999998929. The reversal of 999998921 is 129899999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 667447225 + 332551696 = 25835^2 + 18236^2 .

It is an emirp because it is prime and its reverse (129899999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999998921 - 2² = 999998917 is a prime.

It is not a weakly prime, because it can be changed into another prime (999998929) 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 as a sum of consecutive naturals, namely, 499999460 + 499999461.

It is an arithmetic number, because the mean of its divisors is an integer number (499999461).

Almost surely, 2^999998921 is an apocalyptic number.

It is an amenable number.

999998921 is a deficient number, since it is larger than the sum of its proper divisors (1).

999998921 is an equidigital number, since it uses as much as digits as its factorization.

999998921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8503056, while the sum is 65.

The square root of 999998921 is about 31622.7595411912. The cubic root of 999998921 is about 999.9996403332. Note that the first 3 decimals are identical.

The spelling of 999998921 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, nine hundred twenty-one".