91604021 has 2 divisors, whose sum is σ = 91604022. Its totient is φ = 91604020.

The previous prime is 91604017. The next prime is 91604047. The reversal of 91604021 is 12040619.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 90459121 + 1144900 = 9511^2 + 1070^2 .

It is an emirp because it is prime and its reverse (12040619) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91604021 - 2² = 91604017 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91604321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45802010 + 45802011.

It is an arithmetic number, because the mean of its divisors is an integer number (45802011).

Almost surely, 2^91604021 is an apocalyptic number.

It is an amenable number.

91604021 is a deficient number, since it is larger than the sum of its proper divisors (1).

91604021 is an equidigital number, since it uses as much as digits as its factorization.

91604021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 91604021 is about 9570.9989551770. The cubic root of 91604021 is about 450.7871342861.

The spelling of 91604021 in words is "ninety-one million, six hundred four thousand, twenty-one".