91000020 has 96 divisors (see below), whose sum is σ = 264297600. Its totient is φ = 23376384.

The previous prime is 91000009. The next prime is 91000027. The reversal of 91000020 is 2000019.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91000027) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 397266 + ... + 397494.

It is an arithmetic number, because the mean of its divisors is an integer number (2753100).

Almost surely, 2^91000020 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 91000020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132148800).

91000020 is an abundant number, since it is smaller than the sum of its proper divisors (173297580).

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

91000020 is a wasteful number, since it uses less digits than its factorization.

91000020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457 (or 455 counting only the distinct ones).

The product of its (nonzero) digits is 18, while the sum is 12.

The square root of 91000020 is about 9539.3930624542. The cubic root of 91000020 is about 449.7941774795.

Adding to 91000020 its reverse (2000019), we get a palindrome (93000039).

The spelling of 91000020 in words is "ninety-one million, twenty", and thus it is an aban number and an uban number.