91181820 has 48 divisors (see below), whose sum is σ = 255765888. Its totient is φ = 24271680.

The previous prime is 91181813. The next prime is 91181873. The reversal of 91181820 is 2818119.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 15 ways as a sum of consecutive naturals, for example, 46255 + ... + 48185.

It is an arithmetic number, because the mean of its divisors is an integer number (5328456).

Almost surely, 2^91181820 is an apocalyptic number.

It is an amenable number.

91181820 is an abundant number, since it is smaller than the sum of its proper divisors (164584068).

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

91181820 is a wasteful number, since it uses less digits than its factorization.

91181820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2730 (or 2728 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 91181820 is about 9548.9172161036. The cubic root of 91181820 is about 450.0935114309.

Adding to 91181820 its reverse (2818119), we get a palindrome (93999939).

The spelling of 91181820 in words is "ninety-one million, one hundred eighty-one thousand, eight hundred twenty".