91521821 has 2 divisors, whose sum is σ = 91521822. Its totient is φ = 91521820.

The previous prime is 91521817. The next prime is 91521923. The reversal of 91521821 is 12812519.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46430596 + 45091225 = 6814^2 + 6715^2 .

It is a cyclic number.

It is not a de Polignac number, because 91521821 - 2² = 91521817 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 (91521811) 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, 45760910 + 45760911.

It is an arithmetic number, because the mean of its divisors is an integer number (45760911).

Almost surely, 2^91521821 is an apocalyptic number.

It is an amenable number.

91521821 is a deficient number, since it is larger than the sum of its proper divisors (1).

91521821 is an equidigital number, since it uses as much as digits as its factorization.

91521821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 29.

The square root of 91521821 is about 9566.7037688015. The cubic root of 91521821 is about 450.6522574138.

The spelling of 91521821 in words is "ninety-one million, five hundred twenty-one thousand, eight hundred twenty-one".