11551991 has 6 divisors (see below), whose sum is σ = 12697776. Its totient is φ = 10501700.

The previous prime is 11551979. The next prime is 11551999. The reversal of 11551991 is 19915511.

11551991 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 11551991 - 2¹⁴ = 11535607 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 (11551999) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 47615 + ... + 47856.

It is an arithmetic number, because the mean of its divisors is an integer number (2116296).

Almost surely, 2^11551991 is an apocalyptic number.

11551991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11551991 is a deficient number, since it is larger than the sum of its proper divisors (1145785).

11551991 is an equidigital number, since it uses as much as digits as its factorization.

11551991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95493 (or 95482 counting only the distinct ones).

The product of its digits is 2025, while the sum is 32.

The square root of 11551991 is about 3398.8220018118. The cubic root of 11551991 is about 226.0575140123.

The spelling of 11551991 in words is "eleven million, five hundred fifty-one thousand, nine hundred ninety-one".