91991228 has 24 divisors (see below), whose sum is σ = 187740000. Its totient is φ = 39424224.

The previous prime is 91991209. The next prime is 91991239. The reversal of 91991228 is 82219919.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 32153 + ... + 34896.

It is an arithmetic number, because the mean of its divisors is an integer number (7822500).

Almost surely, 2^91991228 is an apocalyptic number.

91991228 is a gapful number since it is divisible by the number (98) formed by its first and last digit.

It is an amenable number.

91991228 is an abundant number, since it is smaller than the sum of its proper divisors (95748772).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

91991228 is a wasteful number, since it uses less digits than its factorization.

91991228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67074 (or 67058 counting only the distinct ones).

The product of its digits is 23328, while the sum is 41.

The square root of 91991228 is about 9591.2057636149. The cubic root of 91991228 is about 451.4213952858.

The spelling of 91991228 in words is "ninety-one million, nine hundred ninety-one thousand, two hundred twenty-eight".