11991900 has 72 divisors (see below), whose sum is σ = 35247744. Its totient is φ = 3147200.

The previous prime is 11991839. The next prime is 11991911. The reversal of 11991900 is 919911.

It is a super-2 number, since 2×11991900² = 287611331220000, which contains 22 as substring.

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 polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21019 + ... + 21581.

It is an arithmetic number, because the mean of its divisors is an integer number (489552).

Almost surely, 2^11991900 is an apocalyptic number.

11991900 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 11991900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (17623872).

11991900 is an abundant number, since it is smaller than the sum of its proper divisors (23255844).

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

11991900 is a wasteful number, since it uses less digits than its factorization.

11991900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 651 (or 644 counting only the distinct ones).

The product of its (nonzero) digits is 729, while the sum is 30.

The square root of 11991900 is about 3462.9322834846. The cubic root of 11991900 is about 228.8913247752.

The spelling of 11991900 in words is "eleven million, nine hundred ninety-one thousand, nine hundred".