91099978 has 8 divisors (see below), whose sum is σ = 136769220. Its totient is φ = 45510240.

The previous prime is 91099949. The next prime is 91100027. The reversal of 91099978 is 87999019.

It can be written as a sum of positive squares in 2 ways, for example, as 81595089 + 9504889 = 9033^2 + 3083^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16923 + ... + 21646.

Almost surely, 2^91099978 is an apocalyptic number.

91099978 is a deficient number, since it is larger than the sum of its proper divisors (45669242).

91099978 is a wasteful number, since it uses less digits than its factorization.

91099978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39752.

The product of its (nonzero) digits is 367416, while the sum is 52.

The square root of 91099978 is about 9544.6308467117. The cubic root of 91099978 is about 449.9588077521.

The spelling of 91099978 in words is "ninety-one million, ninety-nine thousand, nine hundred seventy-eight".