91085821 has 4 divisors (see below), whose sum is σ = 91424700. Its totient is φ = 90746944.

The previous prime is 91085809. The next prime is 91085831. The reversal of 91085821 is 12858019.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12858019 = 593 ⋅21683.

It can be written as a sum of positive squares in 2 ways, for example, as 49984900 + 41100921 = 7070^2 + 6411^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91085821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91085831) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 169036 + ... + 169573.

It is an arithmetic number, because the mean of its divisors is an integer number (22856175).

Almost surely, 2^91085821 is an apocalyptic number.

It is an amenable number.

91085821 is a deficient number, since it is larger than the sum of its proper divisors (338879).

91085821 is a wasteful number, since it uses less digits than its factorization.

91085821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338878.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 91085821 is about 9543.8891967583. The cubic root of 91085821 is about 449.9354985740.

The spelling of 91085821 in words is "ninety-one million, eighty-five thousand, eight hundred twenty-one".