11531991 has 8 divisors (see below), whose sum is σ = 15393520. Its totient is φ = 7679232.

The previous prime is 11531987. The next prime is 11532011. The reversal of 11531991 is 19913511.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 11531991 - 2² = 11531987 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 (11531921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2055 + ... + 5223.

It is an arithmetic number, because the mean of its divisors is an integer number (1924190).

Almost surely, 2^11531991 is an apocalyptic number.

11531991 is a deficient number, since it is larger than the sum of its proper divisors (3861529).

11531991 is a wasteful number, since it uses less digits than its factorization.

11531991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4385.

The product of its digits is 1215, while the sum is 30.

The square root of 11531991 is about 3395.8785313966. The cubic root of 11531991 is about 225.9269806133.

The spelling of 11531991 in words is "eleven million, five hundred thirty-one thousand, nine hundred ninety-one".