11999991 has 8 divisors (see below), whose sum is σ = 16021744. Its totient is φ = 7989120.

The previous prime is 11999989. The next prime is 12000017. The reversal of 11999991 is 19999911.

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

It is not a de Polignac number, because 11999991 - 2¹ = 11999989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 11999991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11999941) 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, 351 + ... + 4911.

It is an arithmetic number, because the mean of its divisors is an integer number (2002718).

Almost surely, 2^11999991 is an apocalyptic number.

11999991 is a deficient number, since it is larger than the sum of its proper divisors (4021753).

11999991 is an equidigital number, since it uses as much as digits as its factorization.

11999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5441.

The product of its digits is 59049, while the sum is 48.

The square root of 11999991 is about 3464.1003160994. The cubic root of 11999991 is about 228.9427912749.

It can be divided in two parts, 11 and 999991, that multiplied together give a palindrome (10999901).

The spelling of 11999991 in words is "eleven million, nine hundred ninety-nine thousand, nine hundred ninety-one".