11121991 has 4 divisors (see below), whose sum is σ = 11139984. Its totient is φ = 11104000.

The previous prime is 11121989. The next prime is 11122003. The reversal of 11121991 is 19912111.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 11121991 - 2¹ = 11121989 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 (11121491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8035 + ... + 9316.

It is an arithmetic number, because the mean of its divisors is an integer number (2784996).

Almost surely, 2^11121991 is an apocalyptic number.

11121991 is a deficient number, since it is larger than the sum of its proper divisors (17993).

11121991 is an equidigital number, since it uses as much as digits as its factorization.

11121991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17992.

The product of its digits is 162, while the sum is 25.

The square root of 11121991 is about 3334.9649173567. The cubic root of 11121991 is about 223.2171264955.

The spelling of 11121991 in words is "eleven million, one hundred twenty-one thousand, nine hundred ninety-one".