91000000000 has 400 divisors, whose sum is σ = 279726533856. Its totient is φ = 28800000000.

The previous prime is 90999999973. The next prime is 91000000037. The reversal of 91000000000 is 19.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (400).

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a nialpdrome in base 10.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 6999999994 + ... + 7000000006.

Almost surely, 2^91000000000 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 91000000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139863266928).

91000000000 is an abundant number, since it is smaller than the sum of its proper divisors (188726533856).

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

91000000000 is an frugal number, since it uses more digits than its factorization.

91000000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83 (or 27 counting only the distinct ones).

The product of its (nonzero) digits is 9, while the sum is 10.

Adding to 91000000000 its reverse (19), we get a palindrome (91000000019).

The spelling of 91000000000 in words is "ninety-one billion", and thus it is an aban number and an uban number.