12556991 has 4 divisors (see below), whose sum is σ = 12565800. Its totient is φ = 12548184.

The previous prime is 12556969. The next prime is 12556997. The reversal of 12556991 is 19965521.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 12556991 - 2¹⁴ = 12540607 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 (12556997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1721 + ... + 5298.

It is an arithmetic number, because the mean of its divisors is an integer number (3141450).

Almost surely, 2^12556991 is an apocalyptic number.

12556991 is a deficient number, since it is larger than the sum of its proper divisors (8809).

12556991 is an equidigital number, since it uses as much as digits as its factorization.

12556991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8808.

The product of its digits is 24300, while the sum is 38.

The square root of 12556991 is about 3543.5844846709. The cubic root of 12556991 is about 232.4316120595.

The spelling of 12556991 in words is "twelve million, five hundred fifty-six thousand, nine hundred ninety-one".