644789121 has 16 divisors (see below), whose sum is σ = 883775424. Its totient is φ = 417852864.

The previous prime is 644789081. The next prime is 644789129. The reversal of 644789121 is 121987446.

644789121 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644789121 - 2¹⁰ = 644788097 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644789129) 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, 162655 + ... + 166571.

It is an arithmetic number, because the mean of its divisors is an integer number (55235964).

Almost surely, 2^644789121 is an apocalyptic number.

It is an amenable number.

644789121 is a deficient number, since it is larger than the sum of its proper divisors (238986303).

644789121 is a wasteful number, since it uses less digits than its factorization.

644789121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5440.

The product of its digits is 96768, while the sum is 42.

The square root of 644789121 is about 25392.6981827454. The cubic root of 644789121 is about 863.9180882458.

The spelling of 644789121 in words is "six hundred forty-four million, seven hundred eighty-nine thousand, one hundred twenty-one".