11991209021 has 12 divisors (see below), whose sum is σ = 13206900000. Its totient is φ = 10879198440.

The previous prime is 11991209003. The next prime is 11991209039. The reversal of 11991209021 is 12090219911.

It is an interprime number because it is at equal distance from previous prime (11991209003) and next prime (11991209039).

It is a de Polignac number, because none of the positive numbers 2^k-11991209021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11991209051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 38921 + ... + 159678.

It is an arithmetic number, because the mean of its divisors is an integer number (1100575000).

Almost surely, 2^11991209021 is an apocalyptic number.

11991209021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

11991209021 is a deficient number, since it is larger than the sum of its proper divisors (1215690979).

11991209021 is a wasteful number, since it uses less digits than its factorization.

11991209021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199120 (or 199109 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 35.

The spelling of 11991209021 in words is "eleven billion, nine hundred ninety-one million, two hundred nine thousand, twenty-one".