91819091920 has 40 divisors (see below), whose sum is σ = 215593065000. Its totient is φ = 36363993600.

The previous prime is 91819091899. The next prime is 91819091933. The reversal of 91819091920 is 2919091819.

It can be written as a sum of positive squares in 4 ways, for example, as 54829032336 + 36990059584 = 234156^2 + 192328^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5673795 + ... + 5689954.

It is an arithmetic number, because the mean of its divisors is an integer number (5389826625).

Almost surely, 2^91819091920 is an apocalyptic number.

It is an amenable number.

91819091920 is an abundant number, since it is smaller than the sum of its proper divisors (123773973080).

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

91819091920 is a wasteful number, since it uses less digits than its factorization.

91819091920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11363863 (or 11363857 counting only the distinct ones).

The product of its (nonzero) digits is 104976, while the sum is 49.

The spelling of 91819091920 in words is "ninety-one billion, eight hundred nineteen million, ninety-one thousand, nine hundred twenty".