12209991 has 16 divisors (see below), whose sum is σ = 16744320. Its totient is φ = 7911200.

The previous prime is 12209971. The next prime is 12209993. The reversal of 12209991 is 19990221.

It is a cyclic number.

It is not a de Polignac number, because 12209991 - 2⁵ = 12209959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12209993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17536 + ... + 18218.

It is an arithmetic number, because the mean of its divisors is an integer number (1046520).

Almost surely, 2^12209991 is an apocalyptic number.

12209991 is a deficient number, since it is larger than the sum of its proper divisors (4534329).

12209991 is a wasteful number, since it uses less digits than its factorization.

12209991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 846.

The product of its (nonzero) digits is 2916, while the sum is 33.

The square root of 12209991 is about 3494.2797541124. The cubic root of 12209991 is about 230.2705763341.

It can be divided in two parts, 1220 and 9991, that added together give a palindrome (11211).

The spelling of 12209991 in words is "twelve million, two hundred nine thousand, nine hundred ninety-one".