12656991 has 4 divisors (see below), whose sum is σ = 16875992. Its totient is φ = 8437992.

The previous prime is 12656939. The next prime is 12657011. The reversal of 12656991 is 19965621.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 12656991 - 2⁶ = 12656927 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 (12656291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2109496 + ... + 2109501.

It is an arithmetic number, because the mean of its divisors is an integer number (4218998).

Almost surely, 2^12656991 is an apocalyptic number.

12656991 is a deficient number, since it is larger than the sum of its proper divisors (4219001).

12656991 is an equidigital number, since it uses as much as digits as its factorization.

12656991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4219000.

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

The square root of 12656991 is about 3557.6665105094. Note that the first 3 decimals coincide. The cubic root of 12656991 is about 233.0469859255.

It can be divided in two parts, 1265 and 6991, that added together give a triangular number (8256 = T₁₂₈).

The spelling of 12656991 in words is "twelve million, six hundred fifty-six thousand, nine hundred ninety-one".