12778721 has 4 divisors (see below), whose sum is σ = 12795072. Its totient is φ = 12762372.

The previous prime is 12778693. The next prime is 12778729. The reversal of 12778721 is 12787721.

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.

It is a cyclic number.

It is not a de Polignac number, because 12778721 - 2²² = 8584417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12778729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6941 + ... + 8586.

It is an arithmetic number, because the mean of its divisors is an integer number (3198768).

Almost surely, 2^12778721 is an apocalyptic number.

It is an amenable number.

12778721 is a deficient number, since it is larger than the sum of its proper divisors (16351).

12778721 is an equidigital number, since it uses as much as digits as its factorization.

12778721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16350.

The product of its digits is 10976, while the sum is 35.

The square root of 12778721 is about 3574.7336963752. The cubic root of 12778721 is about 233.7917217986.

The spelling of 12778721 in words is "twelve million, seven hundred seventy-eight thousand, seven hundred twenty-one".