91990620728 has 32 divisors (see below), whose sum is σ = 182705783760. Its totient is φ = 43271370240.

The previous prime is 91990620721. The next prime is 91990620763. The reversal of 91990620728 is 82702609919.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 91990620728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91990620721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 181775 + ... + 465857.

Almost surely, 2^91990620728 is an apocalyptic number.

It is an amenable number.

91990620728 is a deficient number, since it is larger than the sum of its proper divisors (90715163032).

91990620728 is a wasteful number, since it uses less digits than its factorization.

91990620728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286487 (or 286483 counting only the distinct ones).

The product of its (nonzero) digits is 979776, while the sum is 53.

The spelling of 91990620728 in words is "ninety-one billion, nine hundred ninety million, six hundred twenty thousand, seven hundred twenty-eight".