97991021 has 2 divisors, whose sum is σ = 97991022. Its totient is φ = 97991020.

The previous prime is 97990993. The next prime is 97991057. The reversal of 97991021 is 12019979.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 88924900 + 9066121 = 9430^2 + 3011^2 .

It is a cyclic number.

It is not a de Polignac number, because 97991021 - 2²⁶ = 30882157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (97991321) 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, 48995510 + 48995511.

It is an arithmetic number, because the mean of its divisors is an integer number (48995511).

Almost surely, 2^97991021 is an apocalyptic number.

It is an amenable number.

97991021 is a deficient number, since it is larger than the sum of its proper divisors (1).

97991021 is an equidigital number, since it uses as much as digits as its factorization.

97991021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 97991021 is about 9899.0414182384. The cubic root of 97991021 is about 461.0295481270.

The spelling of 97991021 in words is "ninety-seven million, nine hundred ninety-one thousand, twenty-one".