11501991 has 12 divisors (see below), whose sum is σ = 16896360. Its totient is φ = 7537680.

The previous prime is 11501881. The next prime is 11502019. The reversal of 11501991 is 19910511.

It is not a de Polignac number, because 11501991 - 2¹⁰ = 11500967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11501491) 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 11 ways as a sum of consecutive naturals, for example, 10300 + ... + 11361.

It is an arithmetic number, because the mean of its divisors is an integer number (1408030).

Almost surely, 2^11501991 is an apocalyptic number.

11501991 is a deficient number, since it is larger than the sum of its proper divisors (5394369).

11501991 is a wasteful number, since it uses less digits than its factorization.

11501991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21726 (or 21723 counting only the distinct ones).

The product of its (nonzero) digits is 405, while the sum is 27.

The square root of 11501991 is about 3391.4585357925. The cubic root of 11501991 is about 225.7308972331.

The spelling of 11501991 in words is "eleven million, five hundred one thousand, nine hundred ninety-one".