91000 has 64 divisors (see below), whose sum is σ = 262080. Its totient is φ = 28800.

The previous prime is 90997. The next prime is 91009. The reversal of 91000 is 19.

91000 = T₃₆ + T₃₇ + ... + T₈₃.

91000 = 111² + 112² + ... + 117².

It is a happy number.

91000 is nontrivially palindromic in base 9.

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 not an unprimeable number, because it can be changed into a prime (91009) 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, 6994 + ... + 7006.

It is an arithmetic number, because the mean of its divisors is an integer number (4095).

2⁹¹⁰⁰⁰ 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 91000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (131040).

91000 is an abundant number, since it is smaller than the sum of its proper divisors (171080).

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

91000 is a wasteful number, since it uses less digits than its factorization.

91000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41 (or 27 counting only the distinct ones).

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

The square root of 91000 is about 301.6620625800. The cubic root of 91000 is about 44.9794144528.

Adding to 91000 its reverse (19), we get a palindrome (91019).

The spelling of 91000 in words is "ninety-one thousand".