91866821 has 4 divisors (see below), whose sum is σ = 91886700. Its totient is φ = 91846944.

The previous prime is 91866799. The next prime is 91866851. The reversal of 91866821 is 12866819.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 73290721 + 18576100 = 8561^2 + 4310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91866821 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 (91866851) 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, 1025 + ... + 13593.

It is an arithmetic number, because the mean of its divisors is an integer number (22971675).

Almost surely, 2^91866821 is an apocalyptic number.

It is an amenable number.

91866821 is a deficient number, since it is larger than the sum of its proper divisors (19879).

91866821 is a wasteful number, since it uses less digits than its factorization.

91866821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19878.

The product of its digits is 41472, while the sum is 41.

The square root of 91866821 is about 9584.7180970543. The cubic root of 91866821 is about 451.2178058845.

The spelling of 91866821 in words is "ninety-one million, eight hundred sixty-six thousand, eight hundred twenty-one".