11728721 has 2 divisors, whose sum is σ = 11728722. Its totient is φ = 11728720.

The previous prime is 11728699. The next prime is 11728751. The reversal of 11728721 is 12782711.

11728721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7980625 + 3748096 = 2825^2 + 1936^2 .

It is a cyclic number.

It is not a de Polignac number, because 11728721 - 2¹⁰ = 11727697 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p₇₇₁₃₈₃ and since 11728721 and 771383 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (11728751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5864360 + 5864361.

It is an arithmetic number, because the mean of its divisors is an integer number (5864361).

Almost surely, 2^11728721 is an apocalyptic number.

It is an amenable number.

11728721 is a deficient number, since it is larger than the sum of its proper divisors (1).

11728721 is an equidigital number, since it uses as much as digits as its factorization.

11728721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1568, while the sum is 29.

The square root of 11728721 is about 3424.7220325159. The cubic root of 11728721 is about 227.2044772084.

The spelling of 11728721 in words is "eleven million, seven hundred twenty-eight thousand, seven hundred twenty-one".