2009645721 has 48 divisors (see below), whose sum is σ = 3116393280. Its totient is φ = 1293304320.

The previous prime is 2009645719. The next prime is 2009645731. The reversal of 2009645721 is 1275469002.

2009645721 is a `hidden beast` number, since 2 + 0 + 0 + 9 + 645 + 7 + 2 + 1 = 666.

2009645721 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 2009645721 - 2¹ = 2009645719 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2009645731) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 928881 + ... + 931041.

It is an arithmetic number, because the mean of its divisors is an integer number (64924860).

Almost surely, 2^2009645721 is an apocalyptic number.

It is an amenable number.

2009645721 is a deficient number, since it is larger than the sum of its proper divisors (1106747559).

2009645721 is an equidigital number, since it uses as much as digits as its factorization.

2009645721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2308 (or 2296 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The square root of 2009645721 is about 44829.0722745854. The cubic root of 2009645721 is about 1261.9432768860.

The spelling of 2009645721 in words is "two billion, nine million, six hundred forty-five thousand, seven hundred twenty-one".