644081439 has 4 divisors (see below), whose sum is σ = 858775256. Its totient is φ = 429387624.

The previous prime is 644081419. The next prime is 644081447. The reversal of 644081439 is 934180446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644081439 - 2⁵ = 644081407 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644081397 and 644081406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644081419) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107346904 + ... + 107346909.

It is an arithmetic number, because the mean of its divisors is an integer number (214693814).

Almost surely, 2^644081439 is an apocalyptic number.

644081439 is a deficient number, since it is larger than the sum of its proper divisors (214693817).

644081439 is a wasteful number, since it uses less digits than its factorization.

644081439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214693816.

The product of its (nonzero) digits is 82944, while the sum is 39.

The square root of 644081439 is about 25378.7596032588. The cubic root of 644081439 is about 863.6019109261.

The spelling of 644081439 in words is "six hundred forty-four million, eighty-one thousand, four hundred thirty-nine".