11991000 has 128 divisors (see below), whose sum is σ = 42831360. Its totient is φ = 2736000.

The previous prime is 11990999. The next prime is 11991011. The reversal of 11991000 is 19911.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20715 + ... + 21285.

It is an arithmetic number, because the mean of its divisors is an integer number (334620).

Almost surely, 2^11991000 is an apocalyptic number.

11991000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 11991000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21415680).

11991000 is an abundant number, since it is smaller than the sum of its proper divisors (30840360).

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

11991000 is a wasteful number, since it uses less digits than its factorization.

11991000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 602 (or 588 counting only the distinct ones).

The product of its (nonzero) digits is 81, while the sum is 21.

The square root of 11991000 is about 3462.8023333711. The cubic root of 11991000 is about 228.8855984836.

It can be divided in two parts, 119 and 91000, that added together give a palindrome (91119).

The spelling of 11991000 in words is "eleven million, nine hundred ninety-one thousand".