13608721 has 27 divisors (see below), whose sum is σ = 17376507. Its totient is φ = 10624320.

The previous prime is 13608719. The next prime is 13608739. The reversal of 13608721 is 12780631.

The square root of 13608721 is 3689.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 10595025 + 3013696 = 3255^2 + 1736^2 .

It is not a de Polignac number, because 13608721 - 2¹ = 13608719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 13608721.

It is not an unprimeable number, because it can be changed into a prime (13608821) 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 26 ways as a sum of consecutive naturals, for example, 438976 + ... + 439006.

Almost surely, 2^13608721 is an apocalyptic number.

13608721 is the 3689-th square number.

13608721 is the 1845-th centered octagonal number.

It is an amenable number.

13608721 is a deficient number, since it is larger than the sum of its proper divisors (3767786).

13608721 is an equidigital number, since it uses as much as digits as its factorization.

13608721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110 (or 55 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The cubic root of 13608721 is about 238.7476488900.

The spelling of 13608721 in words is "thirteen million, six hundred eight thousand, seven hundred twenty-one".