9920021 has 2 divisors, whose sum is σ = 9920022. Its totient is φ = 9920020.

The previous prime is 9919997. The next prime is 9920041. The reversal of 9920021 is 1200299.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6195121 + 3724900 = 2489^2 + 1930^2 .

It is a cyclic number.

It is not a de Polignac number, because 9920021 - 2²² = 5725717 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9920041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4960010 + 4960011.

It is an arithmetic number, because the mean of its divisors is an integer number (4960011).

Almost surely, 2^9920021 is an apocalyptic number.

It is an amenable number.

9920021 is a deficient number, since it is larger than the sum of its proper divisors (1).

9920021 is an equidigital number, since it uses as much as digits as its factorization.

9920021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 9920021 is about 3149.6064833563. The cubic root of 9920021 is about 214.8675658178.

The spelling of 9920021 in words is "nine million, nine hundred twenty thousand, twenty-one".