999997021 has 2 divisors, whose sum is σ = 999997022. Its totient is φ = 999997020.

The previous prime is 999996989. The next prime is 999997049. The reversal of 999997021 is 120799999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 615288025 + 384708996 = 24805^2 + 19614^2 .

It is an emirp because it is prime and its reverse (120799999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999997021 - 2⁵ = 999996989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999997081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499998510 + 499998511.

It is an arithmetic number, because the mean of its divisors is an integer number (499998511).

Almost surely, 2^999997021 is an apocalyptic number.

It is an amenable number.

999997021 is a deficient number, since it is larger than the sum of its proper divisors (1).

999997021 is an equidigital number, since it uses as much as digits as its factorization.

999997021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 826686, while the sum is 55.

The square root of 999997021 is about 31622.7294995230. The cubic root of 999997021 is about 999.9990069990. Note that the first 3 decimals are identical.

The spelling of 999997021 in words is "nine hundred ninety-nine million, nine hundred ninety-seven thousand, twenty-one".