91221211 has 4 divisors (see below), whose sum is σ = 94366800. Its totient is φ = 88075624.

The previous prime is 91221203. The next prime is 91221217. The reversal of 91221211 is 11212219.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 91221211 - 2³ = 91221203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91221217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1572751 + ... + 1572808.

It is an arithmetic number, because the mean of its divisors is an integer number (23591700).

Almost surely, 2^91221211 is an apocalyptic number.

91221211 is a deficient number, since it is larger than the sum of its proper divisors (3145589).

91221211 is a wasteful number, since it uses less digits than its factorization.

91221211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3145588.

The product of its digits is 72, while the sum is 19.

The square root of 91221211 is about 9550.9795832679. The cubic root of 91221211 is about 450.1583163120.

The spelling of 91221211 in words is "ninety-one million, two hundred twenty-one thousand, two hundred eleven".