91089821 has 4 divisors (see below), whose sum is σ = 95050272. Its totient is φ = 87129372.

The previous prime is 91089799. The next prime is 91089833. The reversal of 91089821 is 12898019.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12898019 = 17 ⋅758707.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91089821 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 (91089851) 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, 1980191 + ... + 1980236.

It is an arithmetic number, because the mean of its divisors is an integer number (23762568).

Almost surely, 2^91089821 is an apocalyptic number.

It is an amenable number.

91089821 is a deficient number, since it is larger than the sum of its proper divisors (3960451).

91089821 is a wasteful number, since it uses less digits than its factorization.

91089821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3960450.

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 91089821 is about 9544.0987526324. The cubic root of 91089821 is about 449.9420847277.

The spelling of 91089821 in words is "ninety-one million, eighty-nine thousand, eight hundred twenty-one".