91021288 has 8 divisors (see below), whose sum is σ = 170664930. Its totient is φ = 45510640.

The previous prime is 91021283. The next prime is 91021313. The reversal of 91021288 is 88212019.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 77757124 + 13264164 = 8818^2 + 3642^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (91021283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5688823 + ... + 5688838.

Almost surely, 2^91021288 is an apocalyptic number.

It is an amenable number.

91021288 is a deficient number, since it is larger than the sum of its proper divisors (79643642).

91021288 is a wasteful number, since it uses less digits than its factorization.

91021288 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11377667 (or 11377663 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 91021288 is about 9540.5077433017. The cubic root of 91021288 is about 449.8292158506.

The spelling of 91021288 in words is "ninety-one million, twenty-one thousand, two hundred eighty-eight".