644435219869 has 128 divisors (see below), whose sum is σ = 856719360000. Its totient is φ = 481785796800.

The previous prime is 644435219843. The next prime is 644435219873. The reversal of 644435219869 is 968912534446.

It is not a de Polignac number, because 644435219869 - 2¹⁷ = 644435088797 is a prime.

It is a super-2 number, since 2×644435219869² (a number of 24 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (61) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644435219809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 1538031342 + ... + 1538031760.

It is an arithmetic number, because the mean of its divisors is an integer number (6693120000).

Almost surely, 2^644435219869 is an apocalyptic number.

It is an amenable number.

644435219869 is a deficient number, since it is larger than the sum of its proper divisors (212284140131).

644435219869 is a wasteful number, since it uses less digits than its factorization.

644435219869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844 (or 830 counting only the distinct ones).

The product of its digits is 44789760, while the sum is 61.

The spelling of 644435219869 in words is "six hundred forty-four billion, four hundred thirty-five million, two hundred nineteen thousand, eight hundred sixty-nine".