91663728 has 80 divisors (see below), whose sum is σ = 270045216. Its totient is φ = 26542080.

The previous prime is 91663721. The next prime is 91663777. The reversal of 91663728 is 82736619.

It is a happy number.

It is a Smith number, since the sum of its digits (42) 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 91663728.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91663721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6288 + ... + 14928.

Almost surely, 2^91663728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91663728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (135022608).

91663728 is an abundant number, since it is smaller than the sum of its proper divisors (178381488).

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

91663728 is a wasteful number, since it uses less digits than its factorization.

91663728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8682 (or 8676 counting only the distinct ones).

The product of its digits is 108864, while the sum is 42.

The square root of 91663728 is about 9574.1176094719. The cubic root of 91663728 is about 450.8850532112.

The spelling of 91663728 in words is "ninety-one million, six hundred sixty-three thousand, seven hundred twenty-eight".