644052021 has 16 divisors (see below), whose sum is σ = 912726144. Its totient is φ = 402566144.

The previous prime is 644051999. The next prime is 644052037. The reversal of 644052021 is 120250446.

644052021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 644052021 - 2¹⁵ = 644019253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644051982 and 644052000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644052061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10596 + ... + 37421.

It is an arithmetic number, because the mean of its divisors is an integer number (57045384).

Almost surely, 2^644052021 is an apocalyptic number.

It is an amenable number.

644052021 is a deficient number, since it is larger than the sum of its proper divisors (268674123).

644052021 is a wasteful number, since it uses less digits than its factorization.

644052021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48300.

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 644052021 is about 25378.1800174875. The cubic root of 644052021 is about 863.5887625744.

The spelling of 644052021 in words is "six hundred forty-four million, fifty-two thousand, twenty-one".