12665991 has 16 divisors (see below), whose sum is σ = 18421760. Its totient is φ = 7693920.

The previous prime is 12665987. The next prime is 12666019. The reversal of 12665991 is 19956621.

It is not a de Polignac number, because 12665991 - 2² = 12665987 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12665941) 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, 1026 + ... + 5136.

It is an arithmetic number, because the mean of its divisors is an integer number (1151360).

Almost surely, 2^12665991 is an apocalyptic number.

12665991 is a deficient number, since it is larger than the sum of its proper divisors (5755769).

12665991 is a wasteful number, since it uses less digits than its factorization.

12665991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4206.

The product of its digits is 29160, while the sum is 39.

The square root of 12665991 is about 3558.9311597726. The cubic root of 12665991 is about 233.1022103711.

The spelling of 12665991 in words is "twelve million, six hundred sixty-five thousand, nine hundred ninety-one".