91287221 has 4 divisors (see below), whose sum is σ = 91406700. Its totient is φ = 91167744.

The previous prime is 91287199. The next prime is 91287223. The reversal of 91287221 is 12278219.

It is a happy number.

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 27447121 + 63840100 = 5239^2 + 7990^2 .

It is a cyclic number.

It is not a de Polignac number, because 91287221 - 2¹⁰ = 91286197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91287223) 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, 58586 + ... + 60123.

It is an arithmetic number, because the mean of its divisors is an integer number (22851675).

Almost surely, 2^91287221 is an apocalyptic number.

It is an amenable number.

91287221 is a deficient number, since it is larger than the sum of its proper divisors (119479).

91287221 is a wasteful number, since it uses less digits than its factorization.

91287221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119478.

The product of its digits is 4032, while the sum is 32.

The square root of 91287221 is about 9554.4346248221. The cubic root of 91287221 is about 450.2668721531.

The spelling of 91287221 in words is "ninety-one million, two hundred eighty-seven thousand, two hundred twenty-one".