11813991 has 32 divisors (see below), whose sum is σ = 19622400. Its totient is φ = 6168960.

The previous prime is 11813987. The next prime is 11813993. The reversal of 11813991 is 19931811.

It is a happy number.

It is not a de Polignac number, because 11813991 - 2² = 11813987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11813993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 11061 + ... + 12081.

It is an arithmetic number, because the mean of its divisors is an integer number (613200).

Almost surely, 2^11813991 is an apocalyptic number.

11813991 is a deficient number, since it is larger than the sum of its proper divisors (7808409).

11813991 is a wasteful number, since it uses less digits than its factorization.

11813991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1079.

The product of its digits is 1944, while the sum is 33.

The square root of 11813991 is about 3437.1486729555. The cubic root of 11813991 is about 227.7537546127.

The spelling of 11813991 in words is "eleven million, eight hundred thirteen thousand, nine hundred ninety-one".