12556721 has 4 divisors (see below), whose sum is σ = 12567792. Its totient is φ = 12545652.

The previous prime is 12556711. The next prime is 12556723. The reversal of 12556721 is 12765521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12556721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12556723) 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, 3611 + ... + 6176.

It is an arithmetic number, because the mean of its divisors is an integer number (3141948).

Almost surely, 2^12556721 is an apocalyptic number.

It is an amenable number.

12556721 is a deficient number, since it is larger than the sum of its proper divisors (11071).

12556721 is an equidigital number, since it uses as much as digits as its factorization.

12556721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11070.

The product of its digits is 4200, while the sum is 29.

The square root of 12556721 is about 3543.5463874486. The cubic root of 12556721 is about 232.4299461353.

The spelling of 12556721 in words is "twelve million, five hundred fifty-six thousand, seven hundred twenty-one".