91121221 has 4 divisors (see below), whose sum is σ = 91237792. Its totient is φ = 91004652.

The previous prime is 91121213. The next prime is 91121227. The reversal of 91121221 is 12212119.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 91121221 - 2³ = 91121213 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 (91121227) 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, 57105 + ... + 58678.

It is an arithmetic number, because the mean of its divisors is an integer number (22809448).

Almost surely, 2^91121221 is an apocalyptic number.

It is an amenable number.

91121221 is a deficient number, since it is larger than the sum of its proper divisors (116571).

91121221 is a wasteful number, since it uses less digits than its factorization.

91121221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116570.

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

The square root of 91121221 is about 9545.7436064458. The cubic root of 91121221 is about 449.9937793379.

The spelling of 91121221 in words is "ninety-one million, one hundred twenty-one thousand, two hundred twenty-one".